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Monday, June 16, 2014

SQL Server - Common Table Expressions (CTE)

It's a temporary result set that is defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE, or CREATE VIEW statement. It is not stored as an object and lasts only for the duration of the query. A CTE can be self-referencing and can be referenced multiple times in the same query.


WITH expression_name [ ( column_name [,...n] ) ]


( CTE_query_definition )

SELECT <column_list> FROM expression_name;

Multiple cTE

WITH expression_name1 [ ( column_name [,...n] ) ],
     expression_name2 [ ( column_name [,...n] ) ]   

select <column_list> FROM expression_name1
union all
select <column_list> FROM expression_name2

select <column_list> FROM expression_name1 en1 inner join expression_name2 en2 on en1.column_name= en2.column_name

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