加快这个SQL查询

我有以下（相当传统，做了一年或两年前）SQL查询。 SQL所在的网页（在ASP.NET的SqlDataSource/GridView中使用）非常慢，我已经确定了这个查询的缓慢程度 - 看起来是因为子选择。我已经尝试过使用连接来希望加快速度，但我无法使其工作。有任何想法吗？加快这个SQL查询

我不会把整个查询放在这里，只是因为我在没有互联网访问的机器上工作，所以我将无法复制和粘贴，而大部分只是从主表中选择。

SELECT ..., 
     CASE 
     WHEN di.Total = di.Delivered THEN 'Received' 
     ELSE 'Not Received' END AS 'Status', 
     ... 
FROM Deliveries AS d 
    LEFT OUTER JOIN (
     SELECT Delivery, 
       COUNT(*) AS Total, 
       COUNT(CASE WHEN Status = 2 THEN 1 END) AS Delivered 
     FROM DeliveryItems 
     GROUP BY Delivery 
) AS di ON d.ID = di.Delivery

任何提示？

来源

2011-05-09 Chris

您可以从查询分析器添加执行计划吗？这通常会告诉你导致减速的步骤。 – Keith 2011-05-09 08:23:18

您在DeliveryItems.Delivery和Deliveries.ID上有正确的索引吗？ – spender 2011-05-09 08:25:23

重新标记 - ASP.Net的东西是不相关的，这是纯粹的SQL – RichardW1001 2011-05-09 08:40:30

SELECT Delivery, 
     COUNT(*) AS Total, 
     COUNT(CASE WHEN Status = 2 THEN 1 END) AS Delivered 
FROM DeliveryItems 
GROUP BY Delivery

这部分可以通过开沟CASE语句来改进。也许尝试连接两次，一次是针对总数，一次是针对已过滤的计数。

SELECT ..., 
     CASE 
     WHEN d2.Total = d1.Delivered THEN 'Received' 
     ELSE 'Not Received' END AS 'Status', 
     ... 
FROM Deliveries AS d 

LEFT OUTER JOIN (

SELECT Delivery, 
     COUNT(*) AS Delivered 
FROM DeliveryItems 
WHERE Status = 2 
GROUP BY Delivery) d1 ON d.Id = d1.Delivery 

LEFT OUTER JOIN (

SELECT Delivery, 
     COUNT(*) AS Total 
FROM DeliveryItems 
GROUP BY Delivery) d2 ON d.ID = d2.Delivery

来源

2011-05-09 08:37:46 RichardW1001

加快这个SQL查询

回答

相关问题