How to update SQL field using function and stored procedure? - sql

Question

What I want to do is to update column (NewID) in my table (SampleTable) with the following code, but it's not working.. can somebody help me please? Whats wrong with it?
I have the table 'SampleTable' wich has the fields 'NewID' and 'OldID'.
UPDATE SampleTable SET NewID = dbo.fn_DoStuff(OldID) <-- Not working
My function:
ALTER FUNCTION [dbo].[fn_DoStuff]
(
#int oldid
)
RETURNS int
AS
BEGIN
DECLARE #returnValue int
EXEC #returnValue = dbo.spc_DoStuff #oldid
RETURN #returnValue
END
My stored procedure:
SampleTable1 has the columns ID, SomeColName.
ALTER PROCEDURE [dbo].[spc_GeraAtriðisorðalistaÚrAtriðisorði]
(
#oldid int
)
AS
BEGIN
DECLARE #returnValue int
INSERT INTO SampleTable1 (SomeColName) VALUES (null)
SET #returnValue = ##IDENTITY
INSERT INTO SampleTable2 (SomeColName1, SomeColName2) VALUES (#returnValue, #oldid)
SELECT #returnValue AS RetVal
END

Answer 1

You have 2 problems, the first is you cannot call a stored procedure inside a function, nor can you perform your insert within a function.
The second problem is that even if you could call a stored procedure inside a function, you are not returning the value from the procedure correctly. You would need something like:
CREATE TABLE dbo.T (ID INT IDENTITY, Filler CHAR(10));
GO
CREATE PROCEDURE dbo.Test
AS
DECLARE #i INT;
INSERT dbo.T (Filler) VALUES (NULL);
RETURN SCOPE_IDENTITY();
GO
Note the use of the RETURN statement, if you don't use this the default return value is 0
Then you can use:
DECLARE #i INT;
EXECUTE #i = dbo.Test;
SELECT ReturnVal = #i;
*Note, I have replaced ##IDENTITY with SCOPE_IDENTITY(), ##IDENTITY is rarely the correct function to use*
Example on SQL Fiddle

Answer 2

With your solution GarethD I could still not call the function like I wanted to
UPDATE SampleTable SET NewID = dbo.fn_DoStuff(OldID).
Your code helped me though to start thinking another way. Now I'm using a cursor and a while loop and it works perfectly. See my solution below:
DECLARE #OldID AS INT
DECLARE Upd_CURSOR FOR
SELECT OldID
FROM dbo.SampleTable
WHERE OldID is not null
FOR UPDATE OF NewID
OPEN Upd_CURSOR;
FETCH NEXT FROM Upd_CURSOR INTO #OldID
WHILE ##FETCH_STATUS = 0
BEGIN
DECLARE #returnValue int;
INSERT INTO SampleTable1 (SomeColName) VALUES (null);
SET #returnValue = SCOPE_IDENTITY();
INSERT INTO SampleTable2 (SomeColName1, SomeColName2) VALUES (#returnValue, #OldID)
UPDATE dbo.SampleTable SET NewID = #returnValue WHERE CURRENT OF Upd_CURSOR;
FETCH NEXT FROM Upd_CURSOR INTO #OldID;
END;
CLOSE Upd_CURSOR;
DEALLOCATE Upd_CURSOR;
GO