T-SQL Basics: Variables

T-SQL variables allows you to store and assign values in your T-SQL code.  Variables is a storage unit in programming which allows you to refer back to it at a later time.

T-SQL variables have the following characteristics:

• Local variables must be prefixed @
• Global variables must be prefixed with @@
• Must be declared with the DECLARE statement
• Must specify the data type when declared

Declaring variables

    DECLARE @employeeID INT;
    DECLARE @firstName CHAR(10), @lastName CHAR(20);

As you can see from the above example you can declare a single variable or declare multiple variables with a comma separated list.

Setting variables

  SET @employeeID = 1;
  SET @firstName='Davolio';
  SET @lastName='Nancy';

The above example uses the SET statement assign values to the variables one at a time.

To assign values to multiple variables with one statement you can use the SELECT statement.

SELECT @employeeID=1,@firstName='Dovolio',@lastName='Nancy';

Convert INT Variable To String
 

  Convert(CHAR,@employeeID);