SQL

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;

mySql on duplicate key update

INSERT INTO table (column_list)
VALUES (value_list)
ON DUPLICATE KEY UPDATE
   c1 = v1, 
   c2 = v2,
   ...;

mysql on duplicate key ignore

INSERT INTO table_tags (tag) VALUES ('tag_a'),('tab_b'),('tag_c') ON DUPLICATE KEY UPDATE tag=tag;

mysql on duplicate key update

UPDATE t1 SET c=c+1 WHERE a=1 OR b=2 LIMIT 1;