如果存在更新，否则插入mysql

Question

IF EXISTS (SELECT * FROM two_player  WHERE title='math' and user2 is null)
 UPDATE two_player  SET score2='50' , user2='zahra' WHERE title='math' and user2 is null
 ELSE  
 INSERT INTO two_player  (user1,score1,title) values ('zahra', '50', 'math')

This query works right in sql server. But I am getting this error in the mysql:

*#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IF EXISTS (SELECT * FROM two_player WHERE title='math' and user2 is null) ' at line 1

why?! what is the alternative for that?

Answer 1

You can use Store Procedures to solve this problem like below

    DELIMITER $$
    DROP PROCEDURE IF EXISTS `select_or_insert`$$
    CREATE PROCEDURE select_or_insert()
    begin

    IF EXISTS (SELECT * FROM test WHERE id="id") THEN
       SELECT * FROM test WHERE id="id";
    ELSE
       INSERT INTO test (id,name) VALUES ("id",'name');
    END if;

    END$$

   DELIMITER ;

and call it like this:

call select_or_insert();

Answer 2

Use replace instead update or insert:-

REPLACE INTO two_player  (user1,user2,score1,score2,title) values ('zahra', 'zahra','50','50', 'math')

In this case you must have a unique index.

Else according to your programming language try this:-

UPDATE two_player  SET score2='50' , user2='zahra' WHERE title='math' and user2 is null

if updates_rows == 0:  
      INSERT INTO two_player  (user1,score1,title) values ('zahra', '50', 'math')