T-SQL - function with default parameters
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.
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