Can I use output variables to get a value? - sql-server

Question

I have a stored procedure where I'm checking if username exists and if it does not exists insert into user table then gets userid for the same username. I was trying to use an output variable to get the userid. Am I going about this wrong?
alter Procedure Check_User_Name
(
#username varchar(25),
#password varchar(100),
#role_id integer,
#idn nvarchar output
)
As
Begin
IF NOT EXISTS(SELECT idn=#idn
FROM [user] WHERE username = #username)
BEGIN
INSERT INTO [user] (username,[password],role_id) VALUES
(#username, #password,#role_id)
--select #idn=idn from [user]
Print 'UserName inserted successfully'
End
Else IF EXISTS(SELECT * FROM [user] WHERE username = #username)
Begin
Print 'UserName already exists'
End
END

Answer 1

You had it close -- After replacing your column names to match with what is in my user table, this worked for me. (I think I replaced everything back).
On your Else, you're basically doing a second lookup by username - which is unnecessary in this case.
ALTER Procedure Check_User_Name
(
#username varchar(25),
#password varchar(100),
#role_id integer,
#idn nvarchar(20) output
)
As
Begin
IF NOT EXISTS(SELECT idn
FROM [user] WHERE username = #username)
BEGIN
INSERT INTO [user] (username,[password], role_id) VALUES
(#username, #password)
select #idn=idn from [user] WHERE username = #username
Print 'UserName inserted successfully'
End
Else
Begin
Print 'UserName already exists'
SELECT #idn = idn FROM [user]
WHERE username = #username
End
END
GO
Execute with:
DECLARE #idnOut nVarChar(20)
exec Check_User_Name #username = 'user2127184', #password = 'asdf', #role_id = 0, #idn = #idnOut OUTPUT
SELECT #idnOut

Answer 2

You can use out params, but I always avoid out params in SQL like I do in C# for the same reasons.
If you have a result set with just the UserId:
select #UserId;
then you expand it to include other things later:
select #UserId, #UserGuid;
without much trouble.
Even if you need to return a status (Login Allowed / Locked Out) and details you can just use multiple result sets:
select #Status;
select #UserId; //etc.
If you have out parameters you have to change the Signature of the procedure - which can be a problem if you are supporting multiple clients calling it.
The only change you need to make to the calling code with result sets is to keep finding the new column from the result set.