SQL：输出每个字段值的计数表答案

【问题标题】：SQL: output table of counts per field valueSQL：输出每个字段值的计数表
【发布时间】：2012-07-28 21:20:29
【问题描述】：

我们有以下数据。

TestName  Stage1  Stage2  Stage3  Stage4
Test1     John    Calra   John    Calre
Test2     Calra   null    John    Calra

我们需要实现一个以以下格式显示数据的查询。

User    Stage1count  Stages2Count  Stages3count  Stages4Count
John         1             0             2             0
Calra        1             1             0             2

谢谢约翰

【问题讨论】：

使用子查询。但没有成功。
嗨，约翰。你没有指定一个问题。此外，您的帖子没有显示任何解决问题的尝试，并且看起来您希望其他人为您完成工作。您能否编辑您的问题，让我们了解您尝试过的方法和不适合您的方法？有在FAQ 中发布好问题的提示。

标签： mysql sql sql-server oracle oracle10g

【解决方案1】：

您可以使用union 来规范化数据。之后，常规的pivot 策略将起作用：

select  Name
,       sum(case when Stage = 1 then 1 end) as Stage1count
,       sum(case when Stage = 2 then 1 end) as Stage2count
,       sum(case when Stage = 3 then 1 end) as Stage3count
,       sum(case when Stage = 4 then 1 end) as Stage4count
from    (
        select  1 as Stage
        ,       Stage1 as Name
        from    YourTable
        union all
        select  2 as Stage
        ,       Stage2 as Name
        from    YourTable
        union all
        select  3 as Stage
        ,       Stage3 as Name
        from    YourTable
        union all
        select  4 as Stage
        ,       Stage4 as Name
        from    YourTable
        ) as SubQueryAlias
group by
        Name

【讨论】：

【解决方案2】：

试试这个

 drop table tests
    CREATE TABLE tests(TestName varchar(10),Stage1 varchar(10),Stage2 varchar(10),Stage3 varchar(10),Stage4 varchar(10))
    INSERT INTO tests
    VALUES('Test1','John','Calra','John','Calra'),('Test2','Calra',null,'John','Calra')

select * from tests

    select 'John' as [User] 
          ,SUM(case when stage1='John' then 1 else 0 end) as stage1
          ,SUM(case when stage2='John' then 1 else 0 end) as stage2
          ,SUM(case when stage3='John' then 1 else 0 end) as stage3
          ,SUM(case when stage4='John' then 1 else 0 end) as stage4
    from tests 
    UNION 

    select 'Calra' as [User] 
          ,SUM(case when stage1='Calra' then 1 else 0 end) as stage1
          ,SUM(case when stage2='Calra' then 1 else 0 end) as stage2
          ,SUM(case when stage3='Calra' then 1 else 0 end) as stage3
          ,SUM(case when stage4='Calra' then 1 else 0 end) as stage4
    from tests

【讨论】：