how to create a multi-statement table valued function - sql

Question

I am having a SQL function and I want to return a table, but I'm getting an error:
A RETURN statement with a return value cannot be used in this context.
Here is my query:
ALTER FUNCTION [dbo].[Fnc_GetParentCategories]-- 21
(
#catId int
)
Returns table
As
Begin
Declare #Table table(Id int identity(1,1),Category_Id int,ParentId int);
declare #cid int;
WITH x AS (
SELECT a.Category_Id, a.ParentId
FROM t_Category a
WHERE a.Category_Id=#CatId -- enter dead node walking here
UNION ALL
SELECT b.Category_Id, b.ParentId
FROM t_Category b
JOIN x ON x.Category_Id =b.ParentId
)
insert into #Table select * from x;
return #Table
end
And the error is:
A RETURN statement with a return value cannot be used in this context

Answer 1

Your query is incorrect:
ALTER FUNCTION [dbo].[Fnc_GetParentCategories]-- 21
(
#catId int
)
Returns #Table table
(
Id int identity(1,1),
Category_Id int,
ParentId int
)
AS
Begin
WITH x AS
(
SELECT a.Category_Id, a.ParentId
FROM t_Category a
WHERE a.Category_Id=#CatId -- enter dead node walking here
UNION ALL
SELECT b.Category_Id, b.ParentId
FROM t_Category b
JOIN x ON x.Category_Id =b.ParentId
)
insert into #Table select * from x;
return
end
you declare your table definition just before as

Answer 2

--Transact-SQL Multistatement Table-valued Function Syntax
CREATE FUNCTION [ schema_name. ] function_name
( [ { #parameter_name [ AS ] [ type_schema_name. ] parameter_data_type
[ = default ] [READONLY] }
[ ,...n ]
]
)
RETURNS #return_variable TABLE <table_type_definition>
[ WITH <function_option> [ ,...n ] ]
[ AS ]
BEGIN
function_body
RETURN
END
[ ; ]
Your modified function
ALTER FUNCTION [dbo].[Fnc_GetParentCategories]-- 21
(
#catId int
)
RETURNS #Table TABLE(Id int identity(1,1),Category_Id int,ParentId int)
As
BEGIN
WITH x AS
(
SELECT a.Category_Id, a.ParentId
FROM t_Category a
WHERE a.Category_Id = #CatId -- enter dead node walking here
UNION ALL
SELECT b.Category_Id, b.ParentId
FROM t_Category b
JOIN x ON x.Category_Id = b.ParentId
)
INSERT #Table select * from x;
RETURN
END