SELECT a.dfsname, COUNT(b.dfsid) AS instnum FROM tbl_dfslist a LEFT JOIN tbl_instance b ON a.id = b.dfsid GROUP BY a.id;
(其中tbl_dfslist.id = tbl_instance.dfsid)
SELECT a.dfsname, COUNT(b.dfsid) AS instnum FROM tbl_dfslist a LEFT JOIN tbl_instance b ON a.id = b.dfsid GROUP BY a.id;
(其中tbl_dfslist.id = tbl_instance.dfsid)