On the MySQL SQL statement processing question, why the error in SQL statement w

Have a question to consult, MySQL database, select a.taskid, a.type from TblTask a, TblDepTree b order by b.taskid = a.taskid and b.depType = 2 and a.checkTime desc limit 5; this is the wrong statement obviously, but not carefully implemented, this will influence the performance of database?
DBA says the resulting database performance, make the database becomes long time response, resulting in the concurrency value increases, and had lots of temporary files on disk

Started by Jeremy at November 19, 2016 - 12:09 AM

No table join conditions will have a natural connection CPU consumption of large machine load becomes high

Because the large amounts of data generated by the natural connection order by, will use the temporary table sorting, temporary table in some conditions will produce on the disk that IO blocking machine load becomes high

Posted by Adair at November 24, 2016 - 1:07 AM