What is the difference between SET and SELECT when assigning values to variables, in T-SQL?
Traditionally, SQL Server database developers are accustomed to using SELECT for assigning values to variables. This was fine and a perfectly valid practice right until SQL Server 6.5. Microsoft released SQL Server 7.0 in 1999. SQL Server 7.0 introduced the new SET statement for initializing and assigning values to variables. SQL Server 7.0 Books Online also stated: "It is recommended that SET @local_variable be used for variable assignment rather than SELECT @local_variable."
This caused some confusion in the database developer community, as Microsoft never mentioned, why SET is recommended over SELECT for assigning values to variables. In this article, I will highlight all the major differences between SET and SELECT, and things you should be aware of, when using either SET or SELECT.
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