MySQL重復記錄刪除

      一種詭異的寫法：

delete t  
from t, 
( select table_name,max(id) id 
  from t 
  group by table_name 
  having count(*)>1 ) d 
where t.table_name=d.table_name 
  and t.id<d.id;

      沒見過這種語法，記錄一下。