SQL SERVER Parameter Directions

There are 4 types of parameter direction in SQL SERVER.

1. Input
2. Output or Out
3. InputOutput
4. Return

But we can specify only OUT or OUTPUT as parameter direction for the Procedure or Function.

RETURN at the last statement of the Procedure or Function and not in the parameter declaration of the Procedure or Function.

IN

DECLARE @ParentID int
SET @ParentID =6
exec [dbo].[GetTestTable] @ParentID


ALTER PROCEDURE [dbo].[GetTestTable](
@ParentID INT)
AS
BEGIN
SET @ParentID =10
SELECT @ParentID
END

We can’t able to specify in any where during the execution or in the SP parameter direction.

DECLARE @ParentID int
SET @ParentID =6
exec [dbo].[GetTestTable] @ParentID IN –Not allowed

ALTER PROCEDURE [dbo].[GetTestTable](
@ParentID INT IN) -–Not allowed AS
BEGIN
SELECT @ParentID
END

We will get this error.
Incorrect syntax near the keyword 'in'.

OUTPUT
Output is not only for sending value back to the caller, it also accepts input from the caller. Since by default OUT implies both IN and OUT.

E.g. 1

ALTER PROCEDURE [dbo].[GetTestTable](
@ParentID INT OUTPUT)
AS
BEGIN
SET @ParentID = @ParentID + 5
END


DECLARE @ParentID int
SET @ParentID =6
exec [dbo].[GetTestTable] @ParentID OUT
PRINT @ParentID 

Result: 11

There is no need of RETURN or SELECT statement for the OUT direction parameter. Just assing the value, we will get the result.

If we didn’t assing a new value, we will get only the value we sent during execution of the Procedure or Function.(i.e. 6 for the above condion.)

If we didn’t sent any value during execution of the Procedure or Function we will get only nothing for the below condion.

DECLARE @ParentID int
exec [dbo].[GetTestTable] @ParentID OUT
PRINT @ParentID

E.g. 2

ALTER PROCEDURE [dbo].[GetTestTable](
@ParentID INT OUTPUT)
AS
BEGIN
SET @ParentID =10
SELECT @ParentID
END

No need to pass value. Just specify the keyword OUT near the parameter.

DECLARE @ParentID INT
EXEC [dbo].[GetTestTable] @ParentID OUT
PRINT @ParentID

Result: 10

For the above Procedure or Function we are assigning value to the parameter and also we are using SELECT statement. Here we will get a result-set and aslo the value assigned to our argument.

RETURN

There should be a RETURN statement at the end of the Procedure or Function.

ALTER PROCEDURE [dbo].[GetTestTable](
@ParentID INT OUTPUT)
AS
BEGIN
SET @ParentID =10
RETURN @ParentID
END

DECLARE @ParentID    INT
DECLARE @ReturnValue INT
SET @ParentID     =6
EXEC @ReturnValue = [dbo].[GetTestTable] @ParentID
PRINT @ReturnValue

If there is no RETURN statemnt at the end of the Procedure or Function, we will get only the default value of the RETURN argument datatype.

For example there is no RETURN statemnt for the above Procedure the result will be 0.

We can’t able to return a table variable from a RETURN statement.


Note:

1. By default OUT implies both IN and OUT.
2. Since our parameter is OUT we can pass value, since OUT implies both IN and OUT.
3. The default parameter direction is IN.
4. If the last statement is just RETURN without any value or a variable we will get
   nothing (if we didn’t pass value to the parameter of assign) or default value (if
   we assign value when passing). This is default for all the parameter direction.

These all are wrong.
@ReturnValue EXEC [dbo].[GetTestTable] @ParentID

Line 4: Incorrect syntax near '@ReturnValue'.

@ReturnValue = EXEC [dbo].[GetTestTable] @ParentID

Line 4: Incorrect syntax near '@ReturnValue'.

EXEC [dbo].[GetTestTable] @ParentID, @ReturnValue RETURN

Procedure or Function GetTestTable has too many arguments specified.