Advanced SQL tutorial pdf, Check if data exists, Check if record exists in table for tables - MSDN - Microsoft, check if table has records, Define below transformation in DFD?, Difference between Cached Report and Snapshot Report, Different Ways To Return Data From One Table Which Doesn't Exists In another Table, Download SQL Questions, Download SQL Server Interview Question in PDF, Download SQL SERVER Interview questions, Download SQL Server Interview questions and answers, download sql server interview questions and answers pdf, download sql server interview questions by Pawan Khowal, download sql server interview questions by Pawan Kumar, download sql server interview questions by Pawan Kumar Khowal, Download T-SQL Interview Questions, Finding records in one table not present in another table, Free Download SQL SERVER Interview questions, How to check if a specific record exists in a table in SQL, How to JOIN two table to get missing rows in the second table, How to make connection with a FTP server?, How to select all records from one table that do not exist in another table?, How to show "No Data Found" Message to end user?, NOT IN vs. NOT EXISTS vs. LEFT JOIN / IS NULL, Return only rows where values do not exist in other table, Select rows which are not present in other table, Selecting only values from one table that do NOT exist in another?, SQL, sql - Fastest way to determine if record exists, SQL - find records from one table which don't exist in another, SQL Common Interview Questions, SQL Common Interview Questions and answers, SQL FAQ, SQL FAQs, SQL Interview Q & A, SQL Interview Questions, SQL Not Exists: Filter Out Records that Exist in a Subquery, SQL Queries asked in interviews, SQL Questions, sql server - check if data exist in a table if yes do this else, SQL Server - General Interview Questions and Answers, SQL Server developer Interview questions and answers, SQL Server developer Interview questions with answers, SQL SERVER Indexes, SQL SERVER Interview questions, SQL SERVER Interview questions & Answers, SQL Server Interview questions and answers, SQL Server Interview Questions and Answers - Free PDF, sql server interview questions and answers for net developers, SQL SERVER Tips, SQL Server | Best way to check if data exists in a table ?, SQL SERVER- IF EXISTS(Select null from table) vs IF EXISTS(Select 1 from table), SQL Tips & Tricks, SQL Tips and Tricks, SQL Tricks, T-SQL Server Interview Questions
SQL Server | How to select all records from one table that do not exist in another table? – Different Methods & the Best Method
Today I will talk about how we can fetch records from one table that do not exist in another table. What are the methods available to us and which one these is the best one.? Let’s first create some sample data. Here the ask is find records from tablesA that do not exist in tablesB.
-- CREATE TABLE tablesA ( ID INT ) GO INSERT INTO tablesA VALUES (2),(2),(3),(3) GO CREATE CLUSTERED INDEX Ix_ID ON tablesA(Id) CREATE TABLE tablesB ( ID INT ) GO INSERT INTO tablesB VALUES (2),(2),(NULL) GO CREATE CLUSTERED INDEX Ix_ID ON tablesB(Id) --
Now go through some of the queries written below to fetch records from tablesA that do not exist in tablesB.
-- --Method 1 | NOT IN SELECT ID FROM tablesA WHERE ID NOT IN ( SELECT ID FROM tablesB WHERE tablesA.ID = tablesB.ID ) --Method 2 | NOT EXISTS SELECT ID FROM tablesA WHERE NOT EXISTS ( SELECT ID FROM tablesB WHERE tablesA.ID = tablesB.ID ) --Method 3 | LEFT JOIN SELECT tablesA.ID FROM tablesA LEFT JOIN tablesB ON tablesA.ID = tablesB.ID WHERE tablesB.ID IS NULL --
First lets check the outputs of the above queries. All the above queries are giving proper results.
Now let’s compare the execution plans of all the queries written above then only we can say that which one is performing best out of the lot.
Okay so we got the execution plan, the first two execution plans are identical. Developer/DBA normally don’t use correlation in inside part of the sub query “WHERE tablesA.ID = tablesB.ID”. The last execution plan we have Nested Loop join with a filter operator. The cost taken by all the execution plans are same 33%. This means all are performing almost same in this scenario at least. Now comes the question which one is the best one. Well in this case they are behaving almost same. I always prefer the second one. It scales well and gives out proper output all the time.
That’s all folks; I hope you’ve enjoyed the article and I’ll see you soon with more articles.
Pawan Kumar Khowal
You must be logged in to post a comment.