如何提高查询性能以更快地删除子表记录

Question

我有一个表Order，我想删除clientId 的数据。此表每个客户端有超过 2071458 条记录。而且这个表有16个表的外键引用。哇，当我尝试通过 clientid 删除记录时，删除记录需要 2-4 小时。那么我怎样才能提高性能以更快地做到这一点。如果可以，我可以使用子查询吗？我如何在这个查询中使用。以下是我正在使用的查询。

DECLARE @ORDERID int   
DECLARE DEL_RelDataOFOrdeTab CURSOR FOR  
SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID  
 OPEN DEL_RelDataOFOrdeTab  

  FETCH NEXT FROM DEL_RelDataOFOrdeTab  INTO @ORDERID  
   WHILE @@FETCH_STATUS = 0  

     BEGIN   
       DELETE FROM AUTHORIZED WHERE ORDERID = @ORDERID  
       DELETE FROM AUTODISPALERTS WHERE ORDERID = @ORDERID  
       DELETE FROM DRIVER_REIMBURSEMENT WHERE ORDERID = @ORDERID  
       DELETE FROM FAXPOD WHERE ORDERID = @ORDERID  
       DELETE FROM GENERICFIELDS WHERE ORDERID = @ORDERID  
       DELETE FROM [Messages] WHERE ORDERID = @ORDERID  
       DELETE FROM ORDAUDIT WHERE ORDERID = @ORDERID  
       DELETE FROM OrderNotification WHERE ORDERID = @ORDERID  
       DELETE FROM OrderNotificationActions WHERE ORDERID = @ORDERID  
       DELETE FROM ORDERSPAID WHERE ORDERID = @ORDERID  
       DELETE FROM ROUTESERVERORDERS WHERE ORDERID = @ORDERID  
       DELETE FROM UnfinalizedOrders WHERE ORDERID = @ORDERID  
       print 'DELETING FROM ORDE_'  
       DELETE FROM orde_ where ORDERID = @ORDERID  
       PRINT @ORDERID  
     FETCH NEXT FROM DEL_RelDataOFOrdeTab INTO @ORDERID  
     END  

CLOSE DEL_RelDataOFOrdeTab   
DEALLOCATE DEL_RelDataOFOrdeTab  

DELETE FROM orde_ WHERE CLIENTID = @ClientID   

Answer 1

您可以删除CURSOR，而只使用SUBQUERY。

DELETE FROM AUTHORIZED WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM AUTODISPALERTS WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM DRIVER_REIMBURSEMENT WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM FAXPOD WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM GENERICFIELDS WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM [Messages] WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM ORDAUDIT WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM OrderNotification WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM OrderNotificationActions WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM ORDERSPAID WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM ROUTESERVERORDERS WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM UnfinalizedOrders WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)
DELETE FROM orde_ WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)

基本上，它替换了来自

的WHERE子句

WHERE ORDERID = @ORDERID

到

WHERE ORDERID IN (SELECT ORDERID FROM orde_ WHERE CLIENTID = @ClientID)