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Which Order Should Columns Go in an Index?: Finding All the Red Sweets Part 4
 
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When you create an index on multiple columns there's an important question you need to answer: In which order should you list the columns? This video looks at some of the factors you should consider to help answer this question. ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 3792 The Magic of SQL
Oracle SQL Tutorial 21 - How to Create / Drop Indexes
 
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In the last video, we wrote up the SQL to create three tables: CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, CONSTRAINT users_pk PRIMARY KEY (user_id) ); CREATE TABLE projects( project_id NUMBER, Project_name VARCHAR2(50 CHAR) UNIQUE, creator VARCHAR2(50 CHAR) NOT NULL, CONSTRAINT projects_pk PRIMARY KEY (project_id), CONSTRAINT projects_users_fk FOREIGN KEY (creator) REFERENCES users (username) ON DELETE CASCADE ); CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ); I'm going to increase the size of the users table a bit by adding a first and last name column. CREATE TABLE users( user_id NUMBER, username VARCHAR2(50 CHAR) UNIQUE, first_name VARCHAR2(50 CHAR), last_name VARCHAR2 (50 CHAR), CONSTRAINT users_pk PRIMARY KEY (user_id) ); But before we finish this design, we should consider indexing certain columns. What columns should we index? Well, as a reminder, the columns that are indexed by default are columns with the UNIQUE constraint, and those that are labeled as primary keys. Columns that are not indexed but often should be are those labeled as a foreign key. The column that jumps out the most to me is the creator column of the project table. It's the only foreign key that is not part of some index. Let's fix this by creating our first index. The way we do that is with the CREATE INDEX command. CREATE INDEX projects_creator_ix ON projects (creator) What naming convention are we following for the index? We are naming it by the table name, followed by an underscore, followed by the column, followed by an underscore, followed by an ix (for index). In this situation it does not apply, but if our foreign key column is labeled as UNIQUE, we can add the UNIQUE keyword like this: CREATE UNIQUE INDEX projects_creator_ix ON projects (creator) Now if you want to get rid of an INDEX, you can use this command: DROP INDEX projects_creator_ix Now, if we want to select data from the user table and the project table we can do that much faster. That's because the foreign key and column it references are both indexed and those are the columns we would do the join on. We will discuss how to do joins in a future video. So what are some potential problems with this database design? Overall, it is pretty good. With this design though we need to make sure there is no way for someone to update a user's username. In the next video we are going to discuss why. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me on Patreon! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 7593 Caleb Curry
Database Design 39 - Indexes (Clustered, Nonclustered, Composite Index)
 
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This video covers the basics of indexes. Indexing is an extremely important step of database design. Without Indexes database queries can take a substantial amount of time and hog system resources. The main two classifications of indexes are clustered and non-clustered indexes. Clustered indexes are usually the primary key and determine how the data is actually stored in the table. These are the fastest and most effective. Non-clustered indexes sort a reference to data that is still fast but doesn't actually determine how the data is structured. The best tip I can give you is to use indexes but don't over use them. Having loads of indexes on columns that are barely ever in a where clause or join can bog down the database. This is because every time the table is updated the index must also be updated! When a database looks through a table for certain where conditions on a column that does not have an index, it does an entire table scan. This is not a good practice for large databases (or even small databases but not as bad). With an index the database will do an index seek and quickly find the data you are looking for. Composite indexes consist of two or more columns within one index. Use these when you plan on using the two columns together for a database query WHERE clause. Learn more about indexes here: https://www.calebcurry.com/blogs/database-design/introduction-to-indexes Donate!: http://bit.ly/DonateCTVM2. Courses for Download: http://www.udemy.com/u/calebcurry/ (Use the coupon code "YouTubeDiscount" without the quotes) Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://Twitter.com/calebCurry Subscribe (it's free!): https://www.youtube.com/channel/UCZUyPT9DkJWmS_DzdOi7RIA?sub_confirmation=1 Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 89004 Caleb Curry
SQL Server 33 - Indexes
 
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Indexes allow us to tell the database that certain columns are columns we want to retrieve commonly. This allows the database to optimize retrieval. Additionally, when we get into the SELECT statement, we will often have to join data from multiple tables. When we correctly add indexes to our tables, we can improve the speed of our SELECT and also our joins. There are two types of Index. One is called clustered and the other is called non-clustered. Clustered indexes determine the actual order of the table. By default this is going to be the primary key column. So when you label a column as PRIMARY KEY, you are also going to be creating an INDEX that is a clustered index. A clustered index is kind of like a telephone book, where the data is right there when you look up a phone number. This means that if you are just making a small database that is only going to store a few things, you may be fine. But more likely than not you are going to want to add additional indexes. When you add a new index, you create a non-clustered index. These things do not actually determine the order of the rows in the table. A way of how you can think of how these work is like an index in the back of a book. The index of the book does not actually contain the data, it just tells you where to find it. What columns do you index? You are going to want every primary key to be indexed. What about foreign keys, are they indexed by default? No, they are not. Of all columns, you are probably going to want to index the foreign keys the most because they are used in joins. Lastly, you will likely want to index columns that you are going to use on a regular basis. You can also make composite indexes just like you can make composite keys. You would want to do this when you are going to constantly being using those columns together. There is a lot to learn on multicolumn indexes. We may explore this concept in more detail and see how SQL Server uses them in a future video, but as of right now it's probably more important that we get a general understanding of all things SQL Server before we deep dive on something like that. In the upcoming videos I'll be teaching you how to create indexes. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Support me! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 7191 Caleb Curry
What Impact Do Indexes Have on Inserts?: Finding All the Red Sweets Part 0
 
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Creating indexes can improve query performance. Oracle must maintain the indexes however. This increases the work it must do whenever you modify data in indexed columns. In this video Chris looks at this overhead using a real world analogy - recording the color of all the candies stored in party bags! ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 2548 The Magic of SQL
SQL 12c Tutorial 20 : SQL 12c Creating Multiple Indexes on column
 
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SQL 12c Tutorial 20 : SQL 12c Creating Multiple Indexes on column SQL 12c New Features SQL 12c Tutorial for beginners Oracle 12c Tutorial for beginners Creating Multiple indexes on column
Views: 499 TechLake
SQL tutorial 62: Indexes In Oracle Database By Manish Sharma RebellionRider
 
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Watch and learn concepts of SQL Index In Oracle Database. In this tutorial you will learn about B-Tree Index and Function based Index. ------------------------------------------------------------------------ ►►►LINKS◄◄◄ Blog : Previous Tutorial ► ------------------------------------------------------------------------- ►►►Help Me In Getting A Job◄◄◄ ►Help Me In Getting A Good Job By Connecting With Me on My LinkedIn and Endorsing My Skills. All My Contact Info is Down Below. You Can Also Refer Me To Your Company Thanks ------------------------------------------------------------------------- Copy Cloud referral link || Use this link to join copy cloud and get 20GB of free storage https://copy.com?r=kb4rc1 -------------------------------------------------------------------------- ►Make sure you SUBSCRIBE and be the 1st one to see my videos! -------------------------------------------------------------------------- Amazon Wishlist: http://bit.ly/wishlist-amazon ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ►►►Find me on Social Media◄◄◄ Follow What I am up to as it happens on https://twitter.com/rebellionrider https://www.facebook.com/imthebhardwaj http://instagram.com/rebellionrider https://plus.google.com/+Rebellionrider http://in.linkedin.com/in/mannbhardwaj/ http://rebellionrider.tumblr.com/ http://www.pinterest.com/rebellionrider/ You can also Email me at for E-mail address please check About section Please please LIKE and SHARE my videos it makes me happy. Thanks for liking, commenting, sharing and watching more of our videos This is Manish from RebellionRider.com ♥ I LOVE ALL MY VIEWERS AND SUBSCRIBERS
Views: 39423 Manish Sharma
Indexing in Oracle :B-Tree,Bitmap Indexing
 
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This Video is the 1st tutorial in the video series Indexing in Oracle , The video series explains in detail, What are indexes?It's types, what index should be used in which scenario and other important thing in basic terminology. Note :You may want to watch the video with a higher playback speed(1.25 if it suits you more)
Views: 10308 Tech Coach
How Does the Phyiscal Location of Rows Affect Indexes?: Finding All the Red Sweets Part 2
 
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In part one of the red candy series, Chris compared the efficiency of using a index range scan and full table scan to access data. He found that a full table scan was more efficient when fetching more rows than there are table blocks. This analysis made a big assumption however. It worked on the presumption that there was no correlation between the order of candies in the document and which the bags they were in. In this episode tests this assumption. Chris looks at how the physical order of rows in a table can affect the efficiency of indexes on it. He discusses how Oracle tracks this via the clustering factor. ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 3048 The Magic of SQL
SQL with Oracle 10g XE - Using ALTER TABLE to Modify Table Columns
 
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In this video I use the ALTER TABLE command to modify an existing field column. The command will allow you to change the data types, whether the field can be null, or even the primary key. When using the ALTER TABLE command you would use the keyword MODIFY to make changes to an existing column. Be careful when changing a data type of the null field as existing data may cause an error if not in compliance with the new change. The code I used to alter the Books table is : ALTER TABLE BOOKS MODIFY ISBN_10 VARCHAR(13); This video is part of a series of videos with the purpose of learning the SQL language. For more information visit Lecture Snippets at http://lecturesnippets.com.
Views: 15388 Lecture Snippets
A Story of Indexes and Full Table Scans: Finding All the Red Sweets Part 1
 
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"Why isn't Oracle using my index?!" is a common question people have when tuning SQL queries. In this episode Chris compares two methods for finding all the red candies from party bags he's prepared. He shows how these are like a full table scan and an index range scan. He goes on to compare the performance of these two approaches. He shows when a full table scan becomes more efficient than an index range scan and vice versa. ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 7474 The Magic of SQL
mysql tutorial for beginners (6/8) : Indexes
 
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mysql tutorial for beginners (6/8) : Indexes As things stand, the table students works and can be searched without problem by MySQL—until it grows to more than a couple of hundred rows, At that point, database accesses will get slower and slower with every new row added, because MySQL has to search through every row whenever a query is issued. This is like searching through every book in a library whenever you need to look something up. Of course, you don’t have to search libraries that way, because they have either a card index system or, most likely, a database of their own. The way to achieve fast searches is to add an index, either when creating a table or at any time afterward. But the decision is not so simple. For example, there are different index types such as a regular INDEX, PRIMARY KEY, and FULLTEXT. Also, you must decide which columns require an index, a judgment that requires you to predict whether you will be searching any of the data in that column. And even when you’ve decided that, you still have the option of reducing index size by limiting the amount of each column to be indexed. If we imagine the searches that may be made on the students table, it becomes apparent that all of the columns may need to be searched. Anyway, go ahead and add an index to each of the columns, using the commands: ALTER TABLE students ADD INDEX(name(3)); An alternative to using ALTER TABLE to add an index is to use the CREATE INDEX command. They are equivalent, except that CREATE INDEX cannot be used for creating a PRIMARY KEY CREATE INDEX surname ON students (surname(5)); DESCRIBE students; These commands create indexes on both the name and surname columns, limiting name index to only the first 3 characters, and surname index to the first 5 characters. For instance, when MySQL indexes the following name: SAFAA It will actually store in the index only the first 3 characters: SAF This is done to minimize the size of the index, and to optimize database access speed. DESCRIBE command shows the key MUL for each column. This key means that multiple occurrences of a value may occur within that column, which is exactly what we want, as name or surname may appear many times. You don’t have to wait, until after creating a table to add indexes. In fact, doing so can be time-consuming, as adding an index to a large table can take a very long time. Therefore, let’s look at a command that creates the table students with indexes already in place. CREATE TABLE students ( Id_studnet SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT, name VARCHAR(10) NOT NULL, surname VARCHAR(20) NOT NULL, email VARCHAR(30) NOT NULL, INDEX(name(3)), INDEX(surname(5)), ,PRIMARY KEY(id_studnet),UNIQUE(email)); Another important index, PK, its single unique key for each student to enable instant accessing of a row. The importance of having a key with a unique value for each row will come up when we start to combine data from different tables. You can add PK, while you create the table at the first time, or later by issuing the following command: ALTER TABLE students ADD PRIMARY KEY(id_student); The last important index, FULLTEXT index Unlike a regular index, MySQL’s FULLTEXT allows super-fast searches of entire columns of text. It stores every word in every data string in a special index that you can search using “natural language,” in a similar manner to using a search engine. It’s not strictly true that MySQL stores all the words in a FULLTEXT index, because it has a built-in list of more than 500 words that it chooses to ignore because they are so common that they aren’t very helpful for searching anyway. This list, called stopwords, includes the, as, is, of, and so on. The list helps MySQL run much more quickly when performing a FULLTEXT search and keeps database sizes down. FULLTEXT indexes can be created for CHAR, VARCHAR, and TEXT columns only. A FULLTEXT index definition can be given in the CREATE TABLE statement when a table is created, or added later using ALTER TABLE (or CREATE INDEX). Adding a FULLTEXT index to the table students for the columns name and surname ALTER TABLE classics ADD FULLTEXT(name,surname); this index is in addition to the ones already created and does not affect them You can now perform FULLTEXT searches across this pair of columns. If you find that MySQL is running slower than you think it should be when accessing your database, the problem is usually related to your indexes. Either you don’t have an index where you need one, or the indexes are not optimally designed. Tweaking a table’s indexes will often solve such a problem. In the next tutorial, we will learn about, using FOREIGN KEY Constraints and how to join tables together. Subscribe for more: ---------------------------------------------------------------------------- https://www.youtube.com/subscription_center?add_user=saf3al2a SWE.Safaa Al-Hayali - saf3al2a
Views: 25194 Safaa Al-Hayali
How Many Indexes Are Too Many?: Finding All The Red Sweets Part 5
 
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Every index you add to a table increases its storage requirements and DML overheads. So it's a good idea to create as few as possible. When you have two or more indexes using the same columns, you may be able to get away with just one. But how do you decide which to keep? This video discusses how to analyze your queries so you can cut the number of indexes you create. ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 2092 The Magic of SQL
SQL Queries with Expression Fields (How to put Calculated Columns in a Query)
 
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From chapter 3 of Volume 2 of SQL Queries Joes 2 Pros. This shows how to put calculations as new fields in your queries. You can follow along for free even if you don't have the book. To get the JProCo database on your system watch my other video on "Installing Your Joes2Pros Labs".
SQL: Inroduction to Indexes
 
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In this tutorial, you'll learn what is indexing!, why we need and how we can create indexes...
Views: 23627 radhikaravikumar
Clustered vs. Nonclustered Index Structures in SQL Server
 
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Clustered and nonclustered indexes share many of the same internal structures, but they're fundamentally different in nature. Watch Microsoft Certified IT Professional Jon Seigel explain the similarities and differences of clustered and nonclustered indexes, using a real-world example to show how these structures work to improve the performance of SQL queries. Blog post on primary key vs. the clustered index: http://voluntarydba.com/post/2012/10/02/The-Primary-Key-vs-The-Clustered-Index.aspx CREATE INDEX statement reference: http://technet.microsoft.com/en-us/library/ms188783.aspx ALTER INDEX statement reference: http://technet.microsoft.com/en-us/library/ms188388.aspx Index navigation internals by example: http://sqlblog.com/blogs/paul_white/archive/2011/08/09/sql-server-seeks-and-binary-search.aspx Sample index data is from the AdventureWorksLT2008R2 sample database: http://awlt2008dbscript.codeplex.com/releases/view/46169 Visit my channel for more database administration videos: https://www.youtube.com/voluntarydba Subscribe to get notified about my latest videos: https://www.youtube.com/voluntarydba?sub_confirmation=1 Read additional content on my blog: http://voluntarydba.com Follow on Twitter: https://twitter.com/voluntarydba Like on Facebook: https://facebook.com/voluntarydba
Views: 274903 Voluntary DBA
One SQL Cheat Code For Amazingly Fast JSON Queries - SQL JSON Index performance
 
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How non-persisted computed column indexes make your JSON queries high performance. Did you know that non-persisted columns actually get saved to the index pages? This makes JSON querying incredibly fast in SQL Server. Please like and subscribe if you enjoyed this video! Blog post: https://bertwagner.com/2017/05/09/one-sql-cheat-code-for-amazingly-fast-json-queries/ Want to receive the latest weekly blog posts and videos in your inbox? Sign up for the newsletter here: https://upscri.be/c77fc8/ Elsewhere on the internet: https://bertwagner.com https://twitter.com/bertwagner
Views: 2182 Bert Wagner
How to use the Oracle SQL PIVOT Clause
 
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PIVOT allows you to "flip a table on its side", i.e. Columns to Rows / Rows to Columns. Previously we did this with DECODE or CASE. As of Oracle 11g, Oracle Database includes the PIVOT clause (and UNPIVOT). Oracle expert Geoff Wiland from SkillBuilders will demonstrate PIVOT, UNPIVOT, including the use of aggregate functions.
Views: 9735 SkillBuilders
Get Column Names From a Specific Table  - SQL in Sixty Seconds #083
 
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Question: How to get column names from a specific table in SQL Server? Answer: This is a very popular question and there are multiple ways to get column names of a specific table in SQL Server. Let us see various methods. You can choose the method which you prefer to use for your solutions. Click here to get related scripts discussed in this blog post. https://blog.sqlauthority.com/2017/06/29/sql-server-get-column-names-specific-table/
Views: 7076 Pinal Dave
Oracle Database11g tutorials 8 || SQL DISTINCT with multiple columns |SQL Distinct with Two columns
 
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This SQL tutorial and Oracle database 11g tutorial for beginners will show how to use SQL DISTINCT keyword with SQL Select clause. This Video is in the continuation of previous video on SQL distinct with one column. In this video we will see How to use SQL distinct with multiple columns and SQL distinct with two columns Tool used in this tutorial is SQL developer. This tutorial series is part of SQL expert exam certification training. If you are preparing for SQL certification you can use my tutorials. This SQL Tutorial is a part of free training. Copy Cloud referral link || Use this link to join copy cloud and get 20GB of free storage https://copy.com?r=j7eYO7 Contacts Email [email protected] Twitter https://twitter.com/rebellionrider Instagram http://instagram.com/rebellionrider Facebook. https://www.facebook.com/imthebhardwaj Linkedin. in.linkedin.com/in/mannbhardwaj/ Thanks for linking, commenting, sharing and watching more of our videos This is Manish From The Code makers
Views: 96618 Manish Sharma
Indexes in sql server   Part 35
 
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In this video we will learn about What are indexes Why do we use indexes Advantages of indexes These concepts are applicable to sql server 2000, 2005 and 2008 Text version of the video http://csharp-video-tutorials.blogspot.com/2012/09/indexes-in-sql-server-part-35.html Slides http://csharp-video-tutorials.blogspot.com/2013/08/part-35-indexes.html All SQL Server Text Articles http://csharp-video-tutorials.blogspot.com/p/free-sql-server-video-tutorials-for.html All SQL Server Slides http://csharp-video-tutorials.blogspot.com/p/sql-server.html All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists
Views: 357794 kudvenkat
SQL tutorial 49: CASE - Simple Case Expression in Oracle Database (1/2)
 
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Case expression let you perform IF-THEN-ELSE in oracle database. There are two type of case in oracle simple case expression and searched case expression. This SQL Tutorial 49 is about Simple Case Expression. ● What Is Case Expression ● Syntax of Simple Case Expression ● Query 1. Column name of a table as Search expression in CASE ● Query 2. String as Search expression in CASE Celebrating 1000 subscribers. Thanks a lot guys for all your love and support. ------------------------------------------------------------------------ ►►►LINKS◄◄◄ Blog: http://bit.ly/simple-case-expression ------------------------------------------------------------------------- Copy Cloud referral link || Use this link to join copy cloud and get 20GB of free storage https://copy.com?r=kb4rc1 -------------------------------------------------------------------------- ►Make sure you SUBSCRIBE and be the first one to see my videos! -------------------------------------------------------------------------- Amazon Wishlist: http://bit.ly/wishlist-amazon ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ►►►Find me on Social Media◄◄◄ Follow What I am up to as it happens on https://twitter.com/rebellionrider https://www.facebook.com/imthebhardwaj http://instagram.com/rebellionrider https://plus.google.com/+Rebellionrider http://in.linkedin.com/in/mannbhardwaj/ http://rebellionrider.tumblr.com/ http://www.pinterest.com/rebellionrider/ You can also Email me at [email protected] Please please LIKE and SHARE my videos it makes me happy. Thanks for liking, commenting, sharing and watching more of our videos This is Manish from RebellionRider.com ♥ I LOVE ALL MY VIEWERS AND SUBSCRIBERS
Views: 35649 Manish Sharma
B-Tree Indexes
 
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In this video, I'd like to take a look at B-tree indexes and show how knowing them can help design better database tables and queries.
Oracle Hints Tutorial for improving performance
 
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Oracle Hints Tutorial for improving performance APPEND PARALLEL JOIN INDEX NO_INDEX SELECT /*+ FIRST_ROWS(10) */ * FROM emp WHERE deptno = 10; SELECT /*+ ALL_ROWS */ * FROM emp WHERE deptno = 10; SELECT /*+ NO_INDEX(emp emp_dept_idx) */ * FROM emp, dept WHERE emp.deptno = dept.deptno; SELECT /*+ INDEX(e,emp_dept_idx) */ * FROM emp e WHERE e.deptno = 10; -- SELECT /*+ INDEX(scott.emp,emp_dept_idx) */ * FROM scott.emp; SELECT /*+ AND_EQUAL(e,emp_dept_idx) */ * FROM emp e; SELECT /*+ INDEX_JOIN(e,emp_dept_idx) */ * FROM emp e; SELECT /*+ PARALLEL_INDEX(e,emp_dept_idx , 8) */ * FROM emp e; SELECT /*+ LEADING (dept) */ * FROM emp, dept WHERE emp.deptno = dept.deptno; SELECT /*+ PARALLEL(8) CACHE (e) FULL (e) */ * FROM emp e ; SELECT /*+ PARALLEL FULL (e) */ * FROM emp e ; SELECT /*+ PARALLEL USE_MERGE (emp dept) */ * FROM emp, dept WHERE emp.deptno = dept.deptno; -- SORT Merge Join SELECT /*+ PARALLEL USE_HASH (emp dept) */ * FROM emp, dept WHERE emp.deptno = dept.deptno; -- Hash Join SELECT /*+ PARALLEL */ * FROM emp e ; INSERT /*+ APPEND */ INTO mytmp select /*+ CACHE (e) */ *from emp e; commit;
Views: 4939 TechLake
Oracle Database Indexes: Myths, Tips and Tricks
 
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In this tutorial, OCM John Watson will - via demonstrations - debunk these myths: Myth #1: Oracle Database does not index NULL Myth #2: A search that includes wildcards can't use an index if the wildcard precedes the string. Myth #3: Oracle will not use a function-based index unless the FBI is coded in the predicate. Myth #4: Indexes always help. The more indexes the better. See http://skillbuilders.com/free-oracle-tutorials for gigabytes of free Oracle video tutorials.
Views: 16075 SkillBuilders
Oracle SQL Tutorial 11 - CREATE TABLE
 
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The way you create a table is to use the CREATE TABLE command. CREATE TABLE users() So in this situation, the name comes right after the TABLE keyword. The next thing we do is put all of the columns on a line that we want to put in our table. CREATE TABLE users( user_id, username, first_name, last_name ) Notice the naming conventions here. For this series we are going to make columns with what is known as snake casing. This is where each individual word is separated by an underscore. if you have more than one column, all of them have to have commas except the last one. The comma is a way to say that another column is coming, so you don't need to do it on the last one. Now you would think we were done, but we also have to say what data type each column is. Later we will extensively discuss data types so we can focus on them exclusively. For now, here are the data types we are going to use: CREATE TABLE users( user_id NUMBER, username VARCHAR2(50), first_name VARCHAR2(50), last_name VARCHAR2(50) ) Now, inside of the parenthesis for varchar2, we pass in a number... This is the max length of the string. But the question is, what is it measured in? The default is actually in bytes, not characters. For example if we have the string hello, it is 5 characters, but it might take up a total of 10 bytes of storage. So I would recommend adding the keyword char right after the number so it defaults to 50 characters, not bytes. CREATE TABLE users( user_id NUMBER, username VARCHAR(50 CHAR), first_name VARCHAR2(50 CHAR), last_name VARCHAR2(50 CHAR) ) This will work to create a table, but it's really missing a lot of information… which column is the primary key? Are we adding any indexes? Is there any thing else we need to say about these columns? So as you can tell, we are making progress, but there is still so much to learn. The biggest gotcha to remember from this video is that the data type VARCHAR ends in a 2, stupid, right? who would end the name of something with a 2? Once again, this is Caleb from CalebTheVideoMaker2, and we will catch you in the next one! ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 28291 Caleb Curry
4  When composite index would be used by Oracle
 
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If there is a composite index on any columns then will oracle use it if we give only few of these columns in where clause?
A Story of Index Only Scans: Finding all the Red Sweets Part 3
 
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So far in the red candy series, Chris has compared using an index to a full table scan to access sweets from his table. In this video he asks a different question: What if you just want to count how many sweets are red? In this case the index holds all the information Oracle needs to answer the query. He shows how the optimizer is able to process this via an index only scan. Chris goes on to investigate index only scans further. He discusses how theses can provide better performance than queries accessing the table itself. He finishes by looking at the conditions necessary to enable these. ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 1657 The Magic of SQL
SQL: Indexes - Bit Map & B-trees
 
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In this tutorial, you'll learn when to use b-tree and bitmap index
Views: 52373 radhikaravikumar
How to return multiple values from a function in oracle pl/sql ? (without using out parameter)
 
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This video demonstrates how a function can return multiple values to the calling environment, but without using multiple out parameters, the video shows an example on how we can create a object, a nested table based on the object and then returning the nested table type from the function.
Views: 16981 Kishan Mashru
Get Table Names with Column Names and Data Types in SQL Server - SQL Server Tutorial
 
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In this video ,we will generate the script that will return us all the table names with column names and data type of those columns. We often need this information. Let's say we are going to prepare mapping document for load the data from Source Database to Destination database. We can get the list of all tables with column names and data types from Source Database and Destination Database and then paste in Excel and map the required input columns to output columns for ETL Process. Blog link with scripts used in video http://sqlage.blogspot.com/2015/02/get-all-tables-with-column-names-and.html
Views: 42475 TechBrothersIT
Part 6   Transform rows into columns in sql server
 
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Link for all dot net and sql server video tutorial playlists http://www.youtube.com/user/kudvenkat/playlists Link for slides, code samples and text version of the video http://csharp-video-tutorials.blogspot.com/2014/06/part-6-transform-rows-into-columns-in.html This is another common sql server interview question. We will be using Countries table in this example. SQL to create the table Create Table Countries ( Country nvarchar(50), City nvarchar(50) ) GO Insert into Countries values ('USA','New York') Insert into Countries values ('USA','Houston') Insert into Countries values ('USA','Dallas') Insert into Countries values ('India','Hyderabad') Insert into Countries values ('India','Bangalore') Insert into Countries values ('India','New Delhi') Insert into Countries values ('UK','London') Insert into Countries values ('UK','Birmingham') Insert into Countries values ('UK','Manchester') Here is the interview question. Write a sql query to transpose rows to columns. Using PIVOT operator we can very easily transform rows to columns. Select Country, City1, City2, City3 From ( Select Country, City, 'City'+ cast(row_number() over(partition by Country order by Country) as varchar(10)) ColumnSequence from Countries ) Temp pivot ( max(City) for ColumnSequence in (City1, City2, City3) ) Piv
Views: 179772 kudvenkat
Why Has an Index Broken My Query?
 
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Sometimes Oracle can give unexpected exceptions. This often happens when working with dates stored as strings. In this video, Chris investigates why adding an index to a varchar storing dates could cause a query to fail. He explains why this happens. Then he shows workaround to avoid this. You can download the scripts in this video from LiveSQL at: https://livesql.oracle.com/apex/livesql/file/content_CVN82PZQWQSUFYMOVKG0VI19T.html ============================ The Magic of SQL with Chris Saxon Copyright © 2015 Oracle and/or its affiliates. Oracle is a registered trademark of Oracle and/or its affiliates. All rights reserved. Other names may be registered trademarks of their respective owners. Oracle disclaims any warranties or representations as to the accuracy or completeness of this recording, demonstration, and/or written materials (the “Materials”). The Materials are provided “as is” without any warranty of any kind, either express or implied, including without limitation warranties or merchantability, fitness for a particular purpose, and non-infringement.
Views: 2873 The Magic of SQL
List all tables in a sql server database using a query  Part 65
 
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Text version of the video http://csharp-video-tutorials.blogspot.com/2013/06/part-65-list-all-tables-in-sql-server.html Slides http://csharp-video-tutorials.blogspot.com/2013/09/part-65-list-all-tables-in-sql-server.html All SQL Server Text Articles http://csharp-video-tutorials.blogspot.com/p/free-sql-server-video-tutorials-for.html All SQL Server Slides http://csharp-video-tutorials.blogspot.com/p/sql-server.html All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists In this video we will discuss, writing a transact sql query to list all the tables in a sql server database. This is a very common sql server interview question. Object explorer with in sql server management studio can be used to get the list of tables in a specific database. However, if we have to write a query to achieve the same, there are 3 system views that we can use. 1. SYSOBJECTS - Supported in SQL Server version 2000, 2005 & 2008 2. SYS.TABLES - Supported in SQL Server version 2005 & 2008 3. INFORMATION_SCHEMA.TABLES - Supported in SQL Server version 2005 & 2008 -- Gets the list of tables only Select * from SYSOBJECTS where XTYPE='U' -- Gets the list of tables only Select * from SYS.TABLES -- Gets the list of tables and views select * from INFORMATION_SCHEMA.TABLES To get the list of different object types (XTYPE) in a database Select Distinct XTYPE from SYSOBJECTS Executing the above query on my SAMPLE database returned the following values for XTYPE column from SYSOBJECTS IT - Internal table P - Stored procedure PK - PRIMARY KEY constraint S - System table SQ - Service queue U - User table V - View Please check the following MSDN link for all possible XTYPE column values and what they represent. http://msdn.microsoft.com/en-us/library/ms177596.aspx
Views: 86609 kudvenkat
PIVOT Tutorial - generating dynamic column with PIVOT Interview Question SQL
 
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In this lecture you will learn about PIVOT operator and using it to generate dynamic columns.PIVOT is very use full operator to convert values into columns. PIVOT: •Convert your output from (values)vertical order to horizontal(making columns) one Topic to cover: •PIVOT example •PIVOT syntax •Interview Question •PIVOT on northwind •Dynamic PIVOT query http://www.techsapphire.in/index/pivot_sql_lesson_with_generating_dynamic_columns_with_pivot/0-158
Views: 27242 techsapphire
SQL: pseudo columns (Rowid/Rownum)
 
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In this tutorial, u'll learn the difference between rowid & rownum..
Views: 29811 radhikaravikumar
Oracle SQL Tutorial For Beginners | Oracle SQL Online Training - Session 1
 
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Course : Oracle SQL Online Training Mode of Training : Online Duration : 40 Hours Timings : Flexible Oracle SQL Online Training Demo Registration Link : http://svsoftsolutions.com/demo.aspx Introduction to SQL What is SQL? What Can SQL do? RDBMS SQL Syntax Database Tables SQL Statements Overview of Most Important SQL Commands SELECT UPDATE DELETE INSERT CREATE TABLE ALTER TABLE DROP TABLE CREATE INDEX DROP INDEX SQL SELECT Statement SELECT syntax Demo Database SELECT Column Example SELECT * Example SQL Distinct SELECT DISTINCT Statement SELECT DISTINCT Syntax SELECT DISTINCT Example SQL WHERE Clause WHERE Clause WHERE Clause Example Operators in the WHERE Clause SQL AND & OR Operators AND Operator Example OR Operator Example Combining AND & OR SQL ORDER BY ORDER BY Syntax ORDER BY Example ORDER BY DESC Example ORDER BY Several Column Examples SQL Insert Into INSERT INTO Syntax INSERT INTO Examples Insert Data into Specified Columns SQL UPDATE UPDATE Syntax UPDATE Example Watch out UPDATE statement. SQL DELETE DELETE Syntax DELETE Examples Delete All the Data SQL Aliases SQL Alias Syntax for Columns Alias Example for Table Columns Alias Example for Tables. SQL Joins Different SQL JOINs INNER JOIN LEFT OUTER JOIN RIGHT OUTER JOIN FULL OUTER JOIN SQL UNION UNION Syntax UNION Example UNION ALL Syntax UNION ALL Example SQL Insert Into Select INSERT INTO SELECT Syntax INSERT INTO SELECT Examples SQL Create Table CREATE TABLE Syntax CREATE TABLE Example SQL Constraints CREATE TABLE + CONSTRAINT Syntax NOT NULL Constraint UNIQUE Constraint UNIQUE Constraint on CREATE TABLE UNIQUE Constraint on ALTER TABLE To DROP a UNIQUE Constraint PRIMARY KEY Constraint PRIMARY KEY Constraint on CREATE TABLE PRIMARY KEY Constraint on ALTER TABLE To DROP a PRIMARY KEY Constraint FOREIGN KEY Constraint FOREIGN KEY Constraint on CREATE TABLE FOREIGN KEY Constraint on ALTER TABLE To DROP a FOREIGN KEY Constraint CHECK Constraint CHECK Constraint on CREATE TABLE CHECK Constraint on ALTER TABLE To DROP a CHECK Constraint DEFAULT Constraint on CREATE TABLE DEFAULT Constraint on ALTER TABLE To DROP a DEFAULT Constraint SQL Create Index CREATE INDEX Syntax CREATE UNIQUE INDEX Syntax CREATE INDEX Example SQL DROP Command The DROP INDEX Statement The DROP TABLE Statement The DROP DATABASE Statement The TRUNCATE TABLE Statement SQL ALTER Command The ALTER TABLE Statement ALTER TABLE Example Change Data Type Example DROP COLUMN Example SQL VIEWS CREATE VIEW Statement CREATE VIEW Syntax CREATE VIEW Examples CREATE OR REPLACE VIEW Syntax Dropping a View SQL NULL Values Working with NULL Values IS NULL IS NOT NULL SQL NULL Functions NVL COALESCE For more details visit our website : www.svsoftsolutions.com Or reach us @ USA : +1-845-915-8712 (Toll Free), India : +91-9642373173
Views: 818 SV Soft Solutions
Calculate query performance with Explain Plan in Oracle PLSQL.
 
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Explain plan is a wonderful utility in Oracle PL SQL. It helps you to understand how much cost a query takes to perform based on indexed table or table without index. In this oracle tutorial a full description is given on a table containing huge number of rows first based on index on a column and then without index.
Views: 3605 Subhroneel Ganguly
SQL ORDER BY With Multiple Columns
 
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Jamie King of Neumont University demonstrating ORDER BY in regards to multiple columns.
Views: 6934 Jamie King
ORACLE SQL AND PL/SQL INTERVIEW QUESTION : DIFFERENCE BETWEEN ROWID AND ROWNUM WITH EXAMPLE
 
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In this video tutorial, we discuss the pseudo column rowid and rownum in oracle sql. After watching this video you would be able to understand the basic difference between rowid and a rownum pseudo columns of oracle database. Rowid returns the exact location of the row in the database, hence whenever you retrive a record based on rowid, it is the fastest retrival possible. Whereas for each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle selects the row from a table or set of joined rows. For more such videos visit out complete list of videos on www.youtube.com/c/kishanmashru Visit or blog www.oracleplsqlblog.com
Views: 1620 Kishan Mashru
Oracle SQL Tutorial 20 - How to Create Composite Primary Keys
 
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This video is going to be a tutorial on how to create composite and compound keys. The difference between a composite and compound key is that a composite key can consist of any columns while a compound key has to consist of columns that are all keys themselves. We will be working with a compound key because we are going to be using the an intermediary table that has two foreign keys. The combination of both of the keys have to be unique. First, if we have any other CREATE TABLE commands, we are going to comment those out. We will space out the CREATE TABLE to have each column on a line, then we will add constraints as needed. CREATE TABLE project_users( project_id, user_id ) Now, let's add the data types: CREATE TABLE project_users( project_id NUMBER, user_id NUMBER } Now, what about some column attributes? I'm going to make both of the columns NOT NULL because we always want the rows to have a user and a project: CREATE TABLE project_users( project_id NUMBER NOT NULL, user_id NUMBER NOT NULL } Now, let's add the foreign key constraints. Now, what do we name these? We are going to add a primary key that covers both of these columns, so I'm going to be a sinner and not give these constraints names: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id), user_id NUMBER NOT NULL REFFERENCES users (user_id) ) Now, the way we have it now is that if we delete a project in the project table, and there are any rows in the project_users table, it will throw an error and prevent deletion. I would prefer for it to also delete any project members. That would make sense because if you delete a project we want it to delete the associate between that project and certain users. The same goes for if we delete a user, we want their association with a certain project to be deleted. To do this, we need to add the ON DELETE command: CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, ) Finally, let's learn how to create a compound or composite key. literally, the only difference is that you put a comma and add the second table inside of the parenthesis. CREATE TABLE project_users( project_id NUMBER NOT NULL REFERENCES projects (project_id) ON DELETE CASCADE, user_id NUMBER NOT NULL REFERENCES users (user_id) ON DELETE CASCADE, CONSTRAINT project_users_pk PRIMARY KEY (project_id, user_id) ) Now, the combination of project_id and user_id cannot be null, is always unique, and has an index. The only thing we should do now is add a few indexes. We aren't done yet...In the next video we are going to figure out what columns would benefit from indexes and we'll add them to it. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ HELP ME! http://www.patreon.com/calebcurry Subscribe to my newsletter: http://bit.ly/JoinCCNewsletter Donate!: http://bit.ly/DonateCTVM2. ~~~~~~~~~~~~~~~Additional Links~~~~~~~~~~~~~~~ More content: http://CalebCurry.com Facebook: http://www.facebook.com/CalebTheVideoMaker Google+: https://plus.google.com/+CalebTheVideoMaker2 Twitter: http://twitter.com/calebCurry Amazing Web Hosting - http://bit.ly/ccbluehost (The best web hosting for a cheap price!)
Views: 9453 Caleb Curry
How to use partitioning to improve performance of large tables
 
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In this video we cover in much more detail the improvement in performance that can be achieved by using partitioning. MS SQL server databases can scale well using this feature. We cover how partitioning a table gives similar performance as a single table with a clustered index, we then explore how adding NC index improve performance of the heap table as well as the partitioned table.
Views: 17391 Jayanth Kurup
SQL Server join :- Inner join,Left join,Right join and full outer join
 
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For more such videos visit http://www.questpond.com See our other Step by Step video series below :- Learn Angular tutorial for beginners https://tinyurl.com/ycd9j895 Learn MVC Core step by step :- http://tinyurl.com/y9jt3wkv Learn MSBI Step by Step in 32 hours:- https://goo.gl/TTpFZN Learn Xamarin Mobile Programming Step by Step :- https://goo.gl/WDVFuy Learn Design Pattern Step by Step in 8 hours:- https://goo.gl/eJdn0m Learn C# Step by Step in 100 hours :- https://goo.gl/FNlqn3 Learn Data structures & algorithm in 8 hours :-https://tinyurl.com/ybx29c5s Learn SQL Server Step by Step in 16 hours:- http://tinyurl.com/ja4zmwu Learn Javascript in 2 hours :- http://tinyurl.com/zkljbdl Learn SharePoint Step by Step in 8 hours:- https://goo.gl/XQKHeP Learn TypeScript in 45 Minutes :- https://goo.gl/oRkawI Learn webpack in 50 minutes:- https://goo.gl/ab7VJi Learn Visual Studio code in 10 steps for beginners:- https://tinyurl.com/lwgv8r8 Learn Tableau step by step :- https://tinyurl.com/kh6ojyo Preparing for C# / .NET interviews start here http://www.youtube.com/watch?v=gaDn-sVLj8Q In this video we will try to understand four important concepts Inner joins,Left join,Right join and full outer joins. We are also distributing a 100 page Ebook ".Sql Server Interview Question and Answers". If you want this ebook please share this video in your facebook/twitter/linkedin account and email us on [email protected] with the shared link and we will email you the PDF.
Views: 812973 Questpond
Part 1   How to find nth highest salary in sql
 
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Link for all dot net and sql server video tutorial playlists http://www.youtube.com/user/kudvenkat/playlists Link for slides, code samples and text version of the video http://csharp-video-tutorials.blogspot.com/2014/05/part-1-how-to-find-nth-highest-salary_17.html This is a very common SQL Server Interview Question. There are several ways of finding the nth highest salary. By the end of this video, we will be able to answer all the following questions as well. How to find nth highest salary in SQL Server using a Sub-Query How to find nth highest salary in SQL Server using a CTE How to find the 2nd, 3rd or 15th highest salary Let's use the following Employees table for this demo Use the following script to create Employees table Create table Employees ( ID int primary key identity, FirstName nvarchar(50), LastName nvarchar(50), Gender nvarchar(50), Salary int ) GO Insert into Employees values ('Ben', 'Hoskins', 'Male', 70000) Insert into Employees values ('Mark', 'Hastings', 'Male', 60000) Insert into Employees values ('Steve', 'Pound', 'Male', 45000) Insert into Employees values ('Ben', 'Hoskins', 'Male', 70000) Insert into Employees values ('Philip', 'Hastings', 'Male', 45000) Insert into Employees values ('Mary', 'Lambeth', 'Female', 30000) Insert into Employees values ('Valarie', 'Vikings', 'Female', 35000) Insert into Employees values ('John', 'Stanmore', 'Male', 80000) GO To find the highest salary it is straight forward. We can simply use the Max() function as shown below. Select Max(Salary) from Employees To get the second highest salary use a sub query along with Max() function as shown below. Select Max(Salary) from Employees where Salary [ (Select Max(Salary) from Employees) To find nth highest salary using Sub-Query SELECT TOP 1 SALARY FROM ( SELECT DISTINCT TOP N SALARY FROM EMPLOYEES ORDER BY SALARY DESC ) RESULT ORDER BY SALARY To find nth highest salary using CTE WITH RESULT AS ( SELECT SALARY, DENSE_RANK() OVER (ORDER BY SALARY DESC) AS DENSERANK FROM EMPLOYEES ) SELECT TOP 1 SALARY FROM RESULT WHERE DENSERANK = N To find 2nd highest salary we can use any of the above queries. Simple replace N with 2. Similarly, to find 3rd highest salary, simple replace N with 3. Please Note: On many of the websites, you may have seen that, the following query can be used to get the nth highest salary. The below query will only work if there are no duplicates. WITH RESULT AS ( SELECT SALARY, ROW_NUMBER() OVER (ORDER BY SALARY DESC) AS ROWNUMBER FROM EMPLOYEES ) SELECT SALARY FROM RESULT WHERE ROWNUMBER = 3
Views: 833745 kudvenkat
ROWID VS ROWNUM IN ORACLE
 
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This Video explains the difference between ROWID and ROWNUM using real project examples. ROWID provides the unique physical address where the row is being stored. ROWNUM indicates the order in which the data was returned from the select query.
Views: 2115 Tech Coach
Oracle LISTAGG Function
 
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https://www.databasestar.com/oracle-listagg/ The Oracle LISTAGG function allows you to aggregate or combine string values from multiple rows into a single row. For example, it turns this data: FIRST_NAME Adam Brad Carrie Into this data: FIRST_NAME Adam, Brad, Carrie The same data is shown, but it’s in one row and not multiple. It’s a valuable string manipulation function, and once you know what it is and how it works, you’ll be able to use it in your queries as needed. So what does it look like? The function is: LISTAGG ( measure_expr [, delimiter]) WITHIN GROUP (order_by_clause) [OVER query_partition_clause] These parameters are: measure_expr: This is a column or expression that you want to concatenate the values of. In the example above, it was the first_name column. Mandatory. delimiter: This is the character between each of the measure_expr values. Optional, the default is a comma. order_by_clause: This is the order that the values from the measure_expr are listed. Mandatory. query_partition_clause: This allows you to use LISTAGG as an analytic function, allowing you to show LISTAGG in groups for different rows. One thing to be aware of is that the output of the Oracle LISTAGG function is limited to 4,000 bytes. If you get more than this, you’ll receive an error. The most common way around this that I’ve seen is to write a custom function and use a CLOB. Watch the video to find out more and see some examples. For more information about the Oracle LISTAGG function, including all of the SQL shown in this video and the examples, read the related article here: https://www.databasestar.com/oracle-listagg/
Views: 2222 Database Star
SQL Update Statement using Example in Oracle 11g Database
 
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SQL tutorial for beginners in hindi and english SQL Update Statement using Example in Oracle 11g Database
Alter database table columns without dropping table   Part 67
 
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In this video, we will discuss, altering a database table column without having the need to drop the table. Let's understand this with an example. Text version of the video http://csharp-video-tutorials.blogspot.com/2013/08/part-67-alter-database-table-columns.html Slides http://csharp-video-tutorials.blogspot.com/2013/09/part-67-alter-database-table-columns.html All SQL Server Text Articles http://csharp-video-tutorials.blogspot.com/p/free-sql-server-video-tutorials-for.html All SQL Server Slides http://csharp-video-tutorials.blogspot.com/p/sql-server.html All Dot Net and SQL Server Tutorials in English https://www.youtube.com/user/kudvenkat/playlists?view=1&sort=dd All Dot Net and SQL Server Tutorials in Arabic https://www.youtube.com/c/KudvenkatArabic/playlists We will be using table tblEmployee for this demo. Use the sql script below, to create and populate this table with some sample data. Create table tblEmployee ( ID int primary key identity, Name nvarchar(50), Gender nvarchar(50), Salary nvarchar(50) ) Insert into tblEmployee values('Sara Nani','Female','4500') Insert into tblEmployee values('James Histo','Male','5300') Insert into tblEmployee values('Mary Jane','Female','6200') Insert into tblEmployee values('Paul Sensit','Male','4200') Insert into tblEmployee values('Mike Jen','Male','5500') The requirement is to group the salaries by gender. To achieve this we would write a sql query using GROUP BY as shown below. Select Gender, Sum(Salary) as Total from tblEmployee Group by Gender When you execute this query, we will get an error - Operand data type nvarchar is invalid for sum operator. This is because, when we created tblEmployee table, the "Salary" column was created using nvarchar datatype. SQL server Sum() aggregate function can only be applied on numeric columns. So, let's try to modify "Salary" column to use int datatype. Let's do it using the designer. 1. Right click on "tblEmployee" table in "Object Explorer" window, and select "Design" 2. Change the datatype from nvarchar(50) to int 3. Save the table At this point, you will get an error message - Saving changes is not permitted. The changes you have made require the following tables to be dropped and re-created. You have either made changes to a table that can't be re-created or enabled the option Prevent saving changes that require the table to be re-created. So, the obvious next question is, how to alter the database table definition without the need to drop, re-create and again populate the table with data? There are 2 options Option 1: Use a sql query to alter the column as shown below. Alter table tblEmployee Alter column Salary int Option 2: Disable "Prevent saving changes that require table re-creation" option in sql server 2008 1. Open Microsoft SQL Server Management Studio 2008 2. Click Tools, select Options 3. Expand Designers, and select "Table and Database Designers" 4. On the right hand side window, uncheck, Prevent saving changes that require table re-creation 5. Click OK
Views: 86638 kudvenkat

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