SQL Server查询可提高链接服务器的性能

Question

如何改进下一个SQL Server查询？

SELECT SUM(Qty) 
FROM Products
WHERE Type = 'SODA'
AND (Code LIKE 'A5%'
OR Code IN('DHA2','JHU8','KML2','LQA1','ZSX2')) 

执行需要大量时间.

提前致谢.

我通过Linked Server从DB2数据库获取数据.我不能只是阅读建立索引.

Id   int
Name nvarchar(100)
Type nvarchar(100)
Code nvarchar(100)
Qty  int

Answer 1

首先,尝试创建索引products(type, code, qty).这可能会大大提高性能.

然后,如果这不起作用,请尝试将查询重写为:

select sum(qty)
from ((select qty
       from products
       where type = 'SODA' and
             code like 'A5%'
      ) union all
      (select qty
       from products
       where type = 'SODA' and
             code IN ('DHA2','JHU8','KML2','LQA1','ZSX2'))
      )
     ) t;

这可能看起来更复杂,但有时会or干扰查询优化.