sql - 使 OR 查询更加简化

Question

我正在尝试按 customerType 进行搜索，但遇到了一个小问题:

SELECT DISTINCT CustomerID, CustomerName, City, State, Zip FROM qrySearchFields 
WHERE  CustomerID in (Select CustomerID from tblCustomerTypeLineItems Where CustomerTypeID = 241)

运行时间不到一秒，因此:

SELECT DISTINCT CustomerID, CustomerName, City, State, Zip FROM qrySearchFields 
WHERE CustomerID in (Select CustomerID from tblCustomerTypeLineItems Where CustomerTypeID = 240)

但是当我尝试使用 OR 来同时查找两种类型时:

SELECT DISTINCT CustomerID, CustomerName, City, State, Zip FROM qrySearchFields WHERE
CustomerID in (Select CustomerID from tblCustomerTypeLineItems Where CustomerTypeID = 241) 
Or CustomerID in (Select CustomerID from tblCustomerTypeLineItems Where CustomerTypeID = 240)

大约需要 40 秒。

是否有更好的方法来做到这一点，或者我缺少什么？
有关更多背景信息，请参阅父问题:Displaying Query Results Horizontally

Answer 1

为什么不按如下方式重构您的 OR 查询:

SELECT DISTINCT CustomerID, CustomerName, City, State, Zip 
  FROM qrySearchFields 
 WHERE CustomerID IN (SELECT CustomerID 
                        FROM tblCustomerTypeLineItems 
                       WHERE CustomerTypeID IN (241, 240))

如果您使用的是 SQL Server 2005 及更高版本，则可以使用公用表表达式 (CTE):

WITH cteCustomerId AS 
(
    SELECT CustomerID
      FROM tblCustomerTypeLineItems
     WHERE CustomerTypeID IN (241, 240)
)
SELECT DISTINCT CustomerID, CustomerName, City, State, Zip
  FROM qrySearchFields
 WHERE CustomerID IN (SELECT CustomerID
                        FROM cteCustomerId);