Local Variables in SQL Server

Variables are declared in the body of a batch or procedure with the DECLARE statement and are assigned values by using either a SET or SELECT statement. 

Example :

DECLARE @VarA INT
DECLARE @VarB INT
DECLARE @VarTemp INT
SET @VarA = 1
SET @VarB = 2
SELECT @VarA VarA, @VarB VarB
SELECT @VarTemp = @VarA, @VarA = @VarB, @VarB = @VarTemp
SELECT @VarA VarA, @VarB VarB