T-SQL - function with default parameters

问题:

I have this script:

CREATE FUNCTION dbo.CheckIfSFExists(@param1 INT, @param2 BIT = 1 )
RETURNS BIT
AS
BEGIN
    IF EXISTS ( bla bla bla )
        RETURN 1;
    RETURN 0;
END
GO

I want to use it in a procedure in this way:

IF dbo.CheckIfSFExists( 23 ) = 0
    SET @retValue = 'bla bla bla';

But I get the error:

An insufficient number of arguments were supplied for the procedure or function dbo.CheckIfSFExists.

Why does it not work?

回答1:

you have to call it like this

SELECT dbo.CheckIfSFExists(23, default)

From Technet:

When a parameter of the function has a default value, the keyword DEFAULT must be specified when the function is called in order to retrieve the default value. This behaviour is different from using parameters with default values in stored procedures in which omitting the parameter also implies the default value. An exception to this behaviour is when invoking a scalar function by using the EXECUTE statement. When using EXECUTE, the DEFAULT keyword is not required.

回答2:

You can call it three ways - with parameters, with DEFAULT and via EXECUTE

SET NOCOUNT ON;

DECLARE
@Table  SYSNAME = 'YourTable',
@Schema SYSNAME = 'dbo',
@Rows   INT;

SELECT dbo.TableRowCount( @Table, @Schema )

SELECT dbo.TableRowCount( @Table, DEFAULT )

EXECUTE @Rows = dbo.TableRowCount @Table

SELECT @Rows

回答3:

With user defined functions, you have to declare every parameter, even if they have a default value.

The following would execute successfully:

IF dbo.CheckIfSFExists( 23, default ) = 0
    SET @retValue = 'bla bla bla;

回答4:

One way around this problem is to use stored procedures with an output parameter.

exec sp_mysprocname @returnvalue output, @firstparam = 1, @secondparam=2

values you do not pass in default to the defaults set in the stored procedure itself. And you can get the results from your output variable.