【问题标题】：Is there any built-in function to calculate percentage in SQL Server是否有任何内置函数来计算 SQL Server 中的百分比
【发布时间】：2012-08-30 19:22:38
【问题描述】：

我在编写 SQL 查询以在 % 模式下获取结果时遇到问题，我熟悉 SQL Server 的 SUM() 和 COUNT() 函数，但在查询内部实现逻辑时遇到问题我希望得到以下形式的结果： -

UserName---  % of AccepectResult----   % of RejectResult

我的表结构是这样的，有两列 Name (UserName) 和 Result ：

NAME     Result
---------------
USer1       A
USer1       A
USer1       A
USer1       R
USer1       R
USer1       A
USer2       A
USer2       A
USer2       A
USer2       A
USer2       R

A - Accepted Result
R - Rejected Result

我正在尝试这样写这个查询..

select * into #t1  from 
(
    select UserName , count(Result) as Acc
    from Test where result = 'A'
    group by UserName 
) as tab1

select * into #t2 from 
(
    select UserName , count(Result) as Rej
    from Test where result = 'R'
    group by UserName 
) as tab2

select #t1.UserName , 
      #t1.Acc , 
      #t2.Rej , 
     (#t1.Acc)*100/(#t1.Acc + #t2.Rej)  as AccPercentage,
     (#t2.Rej)*100/(#t1.Acc + #t2.Rej)  as RejPercentage

 from #t1
 inner join #t2 on #t1.UserName = #t2.UserName


drop table #t1

drop table #t2

有没有其他方法可以编写此查询以及在 SQL Server 中计算百分比的任何内置函数？

【问题讨论】：

标签： sql sql-server percentage

【解决方案1】：

您不需要加入表格。相反，您可以像这样使用SUM 或COUNT 函数：

使用SUM函数：

SELECT Name, 100 * 
SUM(CASE WHEN Result = 'A' THEN 1 ELSE 0 END)/COUNT(result)
AS Accept_percent
,100 * 
SUM(CASE WHEN Result = 'R' THEN 1 ELSE 0 END)/COUNT(result)
AS Reject_percent
FROM t
Group by Name;

或者使用COUNT函数：

SELECT Name, 100 * 
COUNT(CASE WHEN Result = 'A' THEN 1 ELSE NULL END)/COUNT(result)
AS Accept_percent
,100 * 
COUNT(CASE WHEN Result = 'R' THEN 1 ELSE NULL END)/COUNT(result)
AS Reject_percent
FROM t
Group by Name;

或者使用SubQuery:

SELECT Name, 100 * 
(SELECT COUNT(result) FROM t WHERE result='A' And Name = main.Name)/COUNT(result)
AS Accept_percent
, 100 * 
(SELECT COUNT(result) FROM t WHERE result='R' And Name = main.Name)/COUNT(result)
AS Reject_percent 
FROM t main
Group by Name;

See this SQLFiddle

【讨论】：

【解决方案2】：

不，没有。您必须乘以 100 并明确除以两个数字。

【讨论】：

【解决方案3】：

试试这样的：

select username, (100 * sum(case result when 'A' then 1 else 0 end) / count(*)) as accepted, 
                 (100 * sum(case result when 'R' then 1 else 0 end) / count(*)) as rejected 
    from test
    group by username

【讨论】：