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This applies to expressions containing variables string concatenation, as demonstrated below, but also to expressions with non-string variables or += style operators. This is because the order and frequency in which the assignments are processed is nondeterminant. For example, may be set to initial value of for all rows. In this case, it is not guaranteed that would be updated on a row by row basis. Antipattern use of recursive variable assignmentĪvoid the following pattern for recursive use of variables and expressions: SELECT = WHERE ProductID = 1000000) -Value does not existĬ. The AdventureWorksLT database is used as the sample database for Azure SQL Database. This example uses the AdventureWorks2019LT sample database, for more information, see AdventureWorks sample databases. In the following example, a subquery is used to assign a value to Because the value requested for CustomerID does not exist, the subquery returns no value and the variable is set to NULL. WHERE ProductID = 1000000 -Value does not exist

The variable retains the "Generic Name" value. The query against the Store table returns no rows because the value specified for CustomerID does not exist in the table. In the following example, the variable is assigned "Generic Name" as its value.

One SELECT statement can initialize multiple local variables.Ī SELECT statement that contains a variable assignment cannot be used to also perform typical result set retrieval operations. If expression is a scalar subquery that returns no value, the variable is set to NULL. If the SELECT statement returns no rows, the variable retains its present value. If the SELECT statement returns more than one value, the variable is assigned the last value that is returned. However, when expression is the name of a column, it can return multiple values. SELECT local_variable is typically used to return a single value into the variable. Is a declared variable for which a value is to be assigned.Īssign the value on the right to the variable on the left.Īssigns the expression that follows, to the variable. To view Transact-SQL syntax for SQL Server 2014 and earlier, see Previous versions documentation.