mysql if not exist

问题

I am coming from MSSQL, and now using Mysql, this may be a easy one but how do you execute a if not exist statement. thanks

IF NOT EXISTS(SELECT * from users WHERE Username = spUsername)
    BEGIN
    INSERT into users(ID,Username,Password,Email,Birthdate,DateJoin)
            VALUES(UUID(),spUsername,spPassword,spEmail,spBirthDate,NOW());
    END

回答1:

Im not a database expert by any means but this is how I do it.

http://www.somethinghitme.com/2010/05/06/mysql-stored-procedures-if-not-exists/

    DECLARE SomeId int;
    DECLARE CheckExists int;
    SET CheckExists = 0;  

    SELECT 1 INTO CheckExists from lookup_table WHERE someField = in_SomeParam LIMIT 1;   

    IF (CheckExists > 0) THEN
        SELECT id INTO SomeId FROM lookup_table WHERE someField = in_SomeParam;
    ELSE
        INSERT INTO lookup_table (someField ) VALUES(in_SomeParam);
        SELECT SomeId = LAST_INSERT_ID();
    END IF; 

来源：https://stackoverflow.com/questions/7113680/mysql-if-not-exist