如何将两个表中的值插入到一个表中？

Question

• 使用 MS Office 2019
• 我在一个协会中有特定数量的成员，每个成员都包含在一个特定的类别中。 我想制作一个表格，统计每个类别中存在和缺席的成员以及协会的总数。 ——
• tblPerson (idPerson , idCategory)
• tblAbsent ( idPerson , idSituation )

tblPerson
-----------------------
idPerson | idCategory |
----------------------+
01       |   03       |
02       |   02       |
03       |   03       |
04       |   01       |
05       |   01       |
06       |   01       |
---------+------------+

tblAbsent
----------------------+
idPerson | idSituation|
----------------------+
01       |   02       |
04       |   01       |
05       |   04       |
06       |   01       |
---------+------------+

我想创建第三个表

• tblTotal (idCategory , tblPerson.COUNT(idCategory) AS total , tblAbsent.COUNT(idCategory) AS 不存在，total-absent AS 存在）

tblTotal
-------------------+--------+---------+
idCategory | total | absent | present |
-----------+-------+--------+---------+
01         |  03   |   03   |   00    |
02         |  01   |   00   |   01    |
03         |  02   |   01   |   01    |
-----------+-------+--------+---------+

Answer 1

您可能会使用以下内容：

select 
    q.idcategory, 
    q.total,
    count(t.idcategory) as absent,
    q.total-count(t.idcategory) as present
from
    (
        select t.idcategory, count(*) as total
        from tblperson t
        group by t.idcategory
    ) q
    left join tblabsent t on q.idcategory = t.idcategory
group by
    q.idcategory, 
    q.total
order by
    q.idcategory

在这里，子查询返回一组不同的idcategory值，以及每个类别中的记录总数。

这个子查询然后被left joined到tblabsent表，并使用count([field])将只计算非空值（而count(*)将计算所有记录）的事实返回缺失/存在记录的总数.

Answer 2

您似乎在表之间具有简单的关系。 我会建议：

select p.idCategory,
       count(*) as total,
       count(a.idPerson) as absent,
       (count(*) - count(a.idPerson)) as present
from tblPerson as p left join
     tblAbsent as a
     on p.idPerson = a.idPerson
group by p.idCategory;

目前还不清楚为什么要在两个表之间重复idCategory 。

Answer 3

select 
    q.idcategory, 
    q.total,
    count(t.idcategory) as absent,
    q.total-count(t.idcategory) as present
from
    (
        select t.idcategory, count(*) as total
        from tblperson t
        group by t.idcategory
    ) q
    left join (select tblAbsent.idPerson as idPerson, tblPerson.idCategory as idCategory FROM tblPerson inner join tblAbsent on tblPerson.idPerson=tblAbsent.idPerson)  t on q.idcategory = t.idcategory
group by
    q.idcategory, 
    q.total
order by
    q.idcategory