Question

我有两个单独的表格，分别代表两个星期的学生出勤情况。我想生成两列，按每周细分每个学生的出勤率。如果一个学生每周出席多次，则应增加出席的次数。另外，如果一个学生在一个星期内出席，而不是在下一个星期内出席，那么该月的出席人数将为1（假设只出席一次），缺席的则为0。我尝试过count（）和join的多种变体，但无济于事。任何帮助将不胜感激。以下是截断的小提琴：

http://www.sqlfiddle.com/#!9/36a6e0

以下是我要达到的目标的一个示例：

Name | CurrWeek | LastWeek

Paula | 0 | 2

Answer 1

您需要加入并计数，并且要合并两个结果集，需要合并

select T1.name,T1.currentwk,T2.lasttwk from 
    (
    select name,count(id) as currentwk from currentWeek

    group by name
    ) as T1

     left  join 
     (

     select name,count(id) as lasttwk from lastWeek

    group by name
       ) as T2
       on T1.name=T2.name

     union 
     select T2.name,T1.currentwk,T2.lasttwk from 
    (
    select name,count(id) as currentwk from currentWeek

    group by name
    ) as T1

     right  join 
     (

     select name,count(id) as lasttwk from lastWeek

    group by name
       ) as T2
       on T1.name=T2.name

http://www.sqlfiddle.com/#!9/36a6e0/25

Answer 2

尝试一下

用于2个表

Select name, max(current_week) current_week, max(last_week) as last_week
    From (
    Select name, count(1) as current_week, 0 as last_week from currentWeek group by name
    union all
    Select name, 0 as current_week, count(1) as last_week from lastWeek group by name
    ) x
    group by name

用于3个表

Select name, max(current_week) current_week, max(last_week) as last_week, max(third_week) as third_week
    From (
    Select name, count(1) as current_week, 0 as last_week, 0 as thrid_week from currentWeek group by name
    union all
    Select name, 0 as current_week, count(1) as last_week, 0 as thrid_week from lastWeek group by name
    union all
    Select name, 0 as current_week, 0 as last_week, count(1) as thrid_week from thirdWeek group by name
    ) x
    group by name

从两个不同的表Sql

2 个答案: