Question

Ok, First off, I am not a mysql guru. Second, I did search, but saw nothing relevant related to mysql, and since my DB knowledge is limited, guessing syntactical differences between two different Database types just isn’t in the cards.

I am trying to determine if a particular value already exists in a table before inserting a row. I’ve decided to go about this using two Stored procedures. The first:

CREATE PROCEDURE `nExists` ( n VARCHAR(255) ) BEGIN
    SELECT COUNT(*) FROM (SELECT * FROM Users WHERE username=n) as T;
END

And The Second:

CREATE PROCEDURE `createUser` ( n VARCHAR(255) ) BEGIN
    IF (nExists(n) = 0) THEN
        INSERT INTO Users...
    END IF;
END

So, as you can see, I’m attempting to call nExists from createUser. I get the error that no Function exists with the name nExists…because it’s a stored procedure. I’m not clear on what the difference is, or why such a difference would be necessary, but I’m a Java dev, so maybe I’m missing some grand DB-related concept here.

Could you guys help me out by any chance?
Thanks

Answer 1

I’m not sure how it helped you, but…

why SELECT COUNT(*) FROM (SELECT * FROM Users WHERE username=n) and not just SELECT COUNT(*) FROM Users WHERE username=n?