MySQL Query Error, sql: SELECT bnid,subject,province,industry,bidtype,city,`declare` FROM bnotice where flag=1 and subject like '%化石燃料%' ORDER BY `declare` DESC LIMIT -30 , 30, ErrMsg: 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 '-30 , 30' at line 1