MySQL Query Error, sql: (SELECT sell_id,price,unit,property_sys_select,property_sys_input,img_path,imp_status,update_date FROM web_sell_4 WHERE sell_id = 29121440 ) UNION (SELECT sell_id,price,unit,property_sys_select,property_sys_input,img_path,imp_status,update_date FROM web_sell_1 WHERE sell_id IN(28703438,28703568)) UNION (SELECT sell_id,price,unit,property_sys_select,property_sys_input,img_path,imp_status,update_date FROM web_sell_3 WHERE sell_id = 18702105 ) UNION (SELECT sell_id,price,unit,property_sys_select,property_sys_input,img_path,imp_status,update_date FROM web_sell_5 WHERE sell_id IN(20081305,21086410,21086369,21086315)) UNION (SELECT sell_id,price,unit,property_sys_select,property_sys_input,img_path,imp_status,update_date FROM web_sell_6 WHERE sell_id = 20564113 ), ErrMsg: MySQL server has gone away