MySQL update in 1 2 3 4 5 6 7 8 9 10 11 12 EXPLAIN UPDATE table0 w SET w.field0 ='foo' WHERE (w.key0,w.key1,w.) IN ( SELECT a.* FROM ( SELECT w1.key0,w1.key1,w1.key2 FROM table0 w1 WHERE w1.field0 IS NULL AND w1.key2=0 LIMIT 10) AS a ); 1 2 3 4 5 6 EXPLAIN UPDATE table0 w0 JOIN (SELECT *FROM table0 w1 WHERE w1.field0 IS NULL AND w1.