When working with stored procedures in SQL Server, it can sometimes be cumbersome to pass values for all the parameters, especially if there are a lot of them. However, SQL Server provides a convenient way to make some parameters required and others optional by assigning them default values.

Let’s take a look at an example:

CREATE PROCEDURE LotsOfParams (
    @Param1 INT,
    @Param2 INT,
    @Param3 INT,
    @Param4 INT=NULL,
    @Param5 INT=0,
    @Param6 INT=5
)
AS
PRINT 1;
GO

In this example, the first three parameters (@Param1, @Param2, and @Param3) are required, while the next three (@Param4, @Param5, and @Param6) are optional. You’ll notice that any valid value is acceptable, including NULL.

Here are some valid examples of executing this stored procedure:

EXEC LotsOfParams 1, 2, 3;
EXEC LotsOfParams 1, 2, 3, 4;
EXEC LotsOfParams @Param1 = 1, @Param3 = 2, @Param2 = 3;

However, these examples are invalid:

EXEC LotsOfParams 1, 2;
EXEC LotsOfParams @Param4 = 1, @Param5 = 2;
EXEC LotsOfParams 1, @Param4 = 1, @Param5 = 2;

When executing the stored procedure, if you don’t specify the parameter names, the values must be passed strictly in the defined order (@Param1, @Param2, etc.). However, if you do specify parameter names, the order doesn’t matter.

Regardless of the order or whether the parameters are named or not, all the required parameters must be provided. This is different from function calls, where there is no way to make a function parameter optional.

But what if you want to have a default value for a parameter while still making it required? In that case, you can use the old-fashioned approach of altering the stored procedure:

ALTER PROCEDURE LotsOfParams (
    @Param1 INT,
    @Param2 INT,
    @Param3 INT,
    @Param4 INT=0,
    @Param5 INT=0,
    @Param6 INT=0
)
AS
IF @Param4 IS NULL
    SET @Param4 = 5;
IF @Param5 IS NULL
    SET @Param5 = 12;
PRINT 1;
GO

In this altered version, the default values for @Param4, @Param5, and @Param6 are set to 0. However, if the values passed for these parameters are NULL, they are then assigned the desired default values (5 for @Param4 and 12 for @Param5).

Understanding how to work with required and optional parameters in SQL Server stored procedures can greatly simplify your code and make it more flexible. By assigning default values to certain parameters, you can reduce the number of values you need to pass when executing the stored procedure.