Stored Procedure

I have the following Stored Procedure:

CREATE PROCEDURE SPR_USER (
CODEUSER VARCHAR(30),
NAME VARCHAR(100),
PASS VARCHAR(20)
AS
BEGIN
INSERT INTO USER
(CODEUSER,NAME,PASS) VALUES
(:CODEUSER,:NAME,PASS);
SUSPEND;
END

I want to change this Stored Procedure to check if allready exists a user with the CODEUSERT that it´s trying to insert before doing the insert or else it´s going to give me an error because the column CODEUSER is a primary key. How can I solve this problem ??

...
IF (NOT EXISTS(SELECT CODEUSER FROM USER WHERE
CODEUSER = :CODEUSER)) THEN
INSERT INTO USER
(CODEUSER,NAME,PASS) VALUES
(:CODEUSER,:NAME,PASS);

btw, do not use SUSPEND in executable procedures, there's no need.

With regards,

Martijn Tonies
Database Workbench - tool for InterBase, Firebird, MySQL, Oracle & MS SQL Server
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But how would the procedure return saying that a user allready exists ?