首选先看看这条语句
DELETE FROM tb_task t WHERE t.`groupname` = 'xxx' AND t.`create_time` > '2013-08-20 14:24:00' AND t.`filter` IS NULL
这句代码在sql里会报错, 由于 tb_task 取了别名 所以,需要在 delete 和from中间 加上别名 t.
详见最后个答案 [http://stackoverflow.com/questions/4471277/mysql-delete-from-with-subquery-as-condition]
mysql manual [http://dev.mysql.com/doc/refman/5.5/en/delete.html]