Question

我在SQL Server 2005中有一个包含sales列的表ID,paymentType,price。

create table sales(id int IDENTITY(1,1),
                   paymentType varchar(2), 
                   price decimal(10,2) default(0)
                  )

有没有办法在一个查询中执行此操作？

SELECT SUM(price) as TE 
FROM sales 
WHERE paymentType = 'E' 

SELECT SUM(price) as TC 
FROM sales 
WHERE paymentType = 'C'

Answer 1

您可以使用GROUP BY按paymentType对值进行分组，并获得两个带有和的“E”和“C”记录

SELECT paymentType,SUM(price) 
FROM sales 
WHERE paymentType = 'E' or paymentType = 'C'
GROUP BY paymentType

Answer 2

您可以使用SUM()和CASE()来实现您的目标。

SELECT  SUM(CASE WHEN paymentType = 'E' THEN price ELSE 0 END) TE,
        SUM(CASE WHEN paymentType = 'C' THEN price ELSE 0 END) TC
FROM    TableName
WHERE   paymentType IN ('E','C')

需要WHERE来过滤特定付款，而不是扫描整个表格。您还需要在列paymentType上添加索引以提高性能。

如何优化此查询？

2 个答案: