Optional parameters in SQL UDF without DEFAULT keyword [duplicate] - sql

Question

This question already has answers here:
Alter a SQL server function to accept new optional parameter
(3 answers)
Closed 8 years ago.
I am looking for a solution, how to create SQL UDF with optional params.
Pseudocode for function where Param1 is necessary and Param2 may be filled (but not needed):
dbo.myFnc(Param1 int [, Param2 int])
Is there a way to create thislike function? For existing built-in sample watch the STR function
STR ( float_expression [ , length [ , decimal ] ] )

Answer 1

You need to pass all arguments to functions, unlike stored procedures. You can use the default keyword to indicate that default value is to be used for the parameter, rather than a user-specified value.
So you can create your function like this:
CREATE FUNCTION dbo.myFnc
(
#param1 int,
#param2 int)
...
and then call the function like this:
dbo.myFnc(Param1, default)

Answer 2

You can define default parameters in the create statement (= default):
--Transact-SQL Inline Table-Valued Function Syntax
CREATE FUNCTION [ schema_name. ] function_name
( [ { #parameter_name [ AS ] [ type_schema_name. ] parameter_data_type
[ = default ] [ READONLY ] }
[ ,...n ]
]
)
RETURNS TABLE
[ WITH <function_option> [ ,...n ] ]
[ AS ]
RETURN [ ( ] select_stmt [ ) ]
[ ; ]
Source MSDN
So you can do something like:
CREATE FUNCTION dbo.myFnc(
#param1 int, -- necessary
#param2 int = 5 -- 5 as default
)
But as shree.pat18 said you need to call the optional function parameter with the "default".
Like:
dbo.myFnc(5, default)

Answer 3

I am not sure which SQL you are referring to, but is it possible to overload the UDF?
dbo.myFnc(Param1 int )
dbo.myFnc(Param1 int , Param2 int)
some sql allows it some doesn't. If yours doesn't, maybe you could try something the could handle null as input
create function func
(
#in1 int,
#in2 int
)
returns int
as
begin
declare #count int
select #count = count(*)
from table
where
field1 = isnull(#in1, field1)
and field2 = isnull(#in2, field2)
return #count
end
go
so you could do something like
select func(null,9)