Question

我正在使用SQL Server 2008。

我正在尝试在一些基本查询中做一些基本的数学运算。我需要加上胜利，损失，总数和百分比。我通常会询问原始数字，然后在将查询返回页面后再进行计算。我想让SQL Server有机会更努力地工作。

我想做的是这样的事情：

SELECT   SUM(case when vote = 1 then 1 else 0 end) as TotalWins,
         SUM(case when vote = 0 then 1 else 0 end) as TotalLosses,
         TotalWins + TotalLosses as TotalPlays,
         TotalPlays / TotalWins  as PctWins

这就是我现在正在做的事情：

SELECT   SUM(case when vote = 1 then 1 else 0 end) as TotalWins,
         SUM(case when vote = 0 then 1 else 0 end) as TotalLosses,
         SUM(case when vote = 1 then 1 else 0 end) + SUM(case when vote = 0 then 1 else 0 end) as Votes

在查询中进行简单数学计算的最简单，最干净的方法是什么？

* 编辑：*

虽然我得到了一些很好的答案，但我没有得到我想要的东西。

我将计算的分数是针对特定团队的，因此，我的结果必须是这样的：

TeamID   Team    Wins   Losses  Totals
1        A's     5      3       8
2        Bee's   7      9       16
3        Seas    1      3       4

SELECT   T.TeamID,
         T.Team,
         V.TotalWins,
         V.TotalLosses,
         V.PctWins
FROM     Teams T 

      JOIN 

     SELECT  V.TeamID,
             SUM(case when vote = 1 then 1 else 0 end) as V.TotWin,
             SUM(case when vote = 0 then 1 else 0 end) as V.TotLoss
     FROM    Votes V
GROUP BY V.TeamID

我试了很多东西，但不知道出了什么问题。我确信JOIN部分是问题所在。如何将这两个结果集组合在一起？

Answer 1

一种方法是将查询包装在外部查询中：

SELECT TotalWins,
       TotalLosses,
       TotalWins + TotalLosses as TotalPlays,
       TotalPlays / TotalWins  as PctWins
FROM
( SELECT SUM(case when vote = 1 then 1 else 0 end) as TotalWins,
         SUM(case when vote = 0 then 1 else 0 end) as TotalLosses
  FROM ...
)

另一种方式（由@Mike Christensen建议）是使用Common Table Expressions (CTE)：

; WITH Calculation AS 
    ( SELECT SUM(case when vote = 1 then 1 else 0 end) as TotalWins,
             SUM(case when vote = 0 then 1 else 0 end) as TotalLosses
      FROM ...
    )

SELECT TotalWins,
       TotalLosses,
       TotalWins + TotalLosses as TotalPlays,
       TotalPlays / TotalWins  as PctWins
FROM
       Calculation

旁注：不知道这是否意味着SQL-Server中的任何性能差异，但您也可以写下这些总和：

SUM(case when vote = 1 then 1 else 0 end)

作为计数：

COUNT(case when vote = 1 then 1 end)    --- the ELSE NULL is implied

Answer 2

试

select a, b, a+b as total
from (
  select
    case ... end as a,
    case ... end as b
  from realtable
) t

Answer 3

要回答第二个问题，这是您提出的修正语法的代码：

SELECT   
    T.TeamID,
    T.Team,
    V.TotalWins,
    V.TotalLosses,
    PctWins  =  V.TotalWins * 100 / CAST(V.TotalWins + V.TotalLosses AS float)
FROM Teams T 
JOIN  (
    SELECT  
        TeamID,
        SUM(case when vote = 1 then 1 else 0 end) as TotalWins,
        SUM(case when vote = 0 then 1 else 0 end) as TotalLosses
    FROM Votes
    GROUP BY TeamID
    ) as V on T.TeamID = V.TeamID

注意内部选择的括号。

Answer 4

如果你不止一次做这种事情来创建一个视图，它可能会有所帮助......

CREATE VIEW [Totals]
SELECT   
    SUM(case when T.vote = 1 then 1 else 0 end) as TotalWins,
    SUM(case when T.vote = 0 then 1 else 0 end) as TotalLosses,
    T.SomeGroupColumn
FROM SomeTable T
GROUP BY T.SomeGroupColumn

如何在查询中添加和划分别名列？

4 个答案: