how mysql update on duplicate key works code example
Example 1: mysql on duplicate key update
INSERT INTO t1 (a,b,c) VALUES (1,2,3)
ON DUPLICATE KEY UPDATE c=3;
INSERT INTO t1 (a,b,c) VALUES (4,5,6)
ON DUPLICATE KEY UPDATE c=9;
Example 2: mysql on duplicate key update
UPDATE t1 SET c=c+1 WHERE a=1 OR b=2 LIMIT 1;