Why we use CTE in sql server?

Question

Any body can suggest me what is the best use of CTE in sql server.

SAM ROCK · Answer

Thanks Bhushan Bhasme

SAM ROCK · Answer

Thanks Francis

Bhushan Bhasme · Answer

Hi Sam A common table expression (CTE) can be thought of as a temporary result set that is defined within the execution scope of a single SELECT INSERT UPDATE DELETE or CREATE VIEW statement. A CTE is similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. Unlike a derived table a CTE can be self-referencing and can be referenced multiple times in the same query. A CTE can be used to: Create a recursive query. For more information see Recursive Queries Using Common Table Expressions Substitute for a view when the general use of a view is not required; that is you do not have to store the definition in metadata. Enable grouping by a column that is derived from a scalar subselect or a function that is either not deterministic or has external access. Reference the resulting table multiple times in the same statement. Using a CTE offers the advantages of improved readability and ease in maintenance of complex queries. The query can be divided into separate simple logical building blocks. These simple blocks can then be used to build more complex interim CTEs until the final result set is generated. CTEs can be defined in user-defined routines such as functions stored procedures triggers or views. For More Info Please Visit Below Link https://technet.microsoft.com/en-us/library/ms190766%28v=sql.105%29.aspx

Francis · Answer

CTE can be used in the below scenarios: 1) If you want to store the result of the query that lasts only the duration of the query. 2) If you want to self-reference it in the query. In the above 2 scenarios you can use Derived tables also but it won't give the above flexibility. In that case you can go with CTE. Hope this helps a bit!