MySQL stored procedure, handling multiple cursors and query results

Question

How can I use two cursors in the same routine? If I remove the second cursor declaration and fetch loop everthing works fine. The routine is used for adding a friend in my webap

Answer 1

Rather than using cursors to check for the existence of records, you can use the EXISTS clause in the WHERE clause:

INSERT INTO users_friends 
  (user_id, friend_id) 
VALUES
  (inUserId, tempFriendId)
WHERE EXISTS(SELECT NULL 
               FROM users 
              WHERE email = inFriendEmail)
  AND NOT EXISTS(SELECT NULL 
                   FROM users_friends 
                  WHERE user_id = tempFriendId 
                    AND friend_id = tempFriendId);

I made an alteration after reading Paul's comments about the second query, and reversed the logic so the insert won't add duplicates. Ideally this should be handled as a primary key being a compound key (including two or more columns), which would stop the need for checking in code.