Question

我计划做的是它会从两个表（tblshoes，tblpants）获取过去一个月的所有记录，并计算发生了多少订单，因为这将在谷歌图表折线图上使用我试图获得所有数据从7月30日到1日

SELECT COUNT(*) AS shoeorder, EXTRACT(DAY FROM tlDate) as pdate
FROM tblshoes
WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
GROUP BY EXTRACT(DAY FROM tlDate)

以下是我的表格：

 tblshoes

sname                            tlDate
Name Here                        2017-07-15
Name Again                       2017-07-14
Name again and again             2017-07-13
Name im tired                    2017-07-15
Name of a patient                2017-07-10
.....

tblpants

    pname                            tlDate
    Name Here                        2017-07-15
    Name Again                       2017-07-14
    Name again and again             2017-07-13
    Name im tired                    2017-07-15
    Name of a patient                2017-07-10

结果：

shoeorder                      pdate
2                          15
1                          14
1                          13
1                          10

我想要的是什么：

shoeorder           pdate            pantorder
0                   30                 0
0                   29                 0
0                   28                 0
0                   27                 0
0                   26                 0
0                   25                 0
0                   24                 0
0                   23                 0
0                   22                 0
0                   21                 0
0                   20                 0
0                   19                 0
0                   18                 0
0                   17                 0
0                   16                 0
2                   15                 2
1                   14                 1
1                   13                 1
0                   12                 0
0                   11                 0
1                   10                 1
0                    9                 0
0                    8                 0
0                    7                 0
0                    6                 0 
0                    5                 0
0                    4                 0
0                    3                 0
0                    2                 0
0                    1                 0

Answer 1

SELECT COUNT(*) AS shoeorder, EXTRACT(DAY FROM tlDate) as pdate
FROM (select tlDate from tblshoes
      union all
      select tlDate from tblpants) sub
WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
GROUP BY EXTRACT(DAY FROM tlDate)

猜猜你应该将两个表合并，然后将group by应用于结果查询

更新：然后你需要一个填满所有日期的表（每天）。使用该表并左键加入查询。

SELECT COUNT(*) AS shoeorder, EXTRACT(DAY FROM adt.tlDate) as pdate
FROM all_days_table adt 
      LEFT JOIN (select tlDate from tblshoes
                 union all
                 select tlDate from tblpants) sub ON adt.tlDate = sub.tlDate
WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
GROUP BY EXTRACT(DAY FROM adt.tlDate)

Answer 2

您需要使用完全外部联接...

select
   coalesce(a.shoeorder, 0) as shoeorder
  ,coalesce(a.pdate, b.pdate) as pdate
  ,coalesce(b.pantorder, 0) as pantorder
from (
  SELECT COUNT(*) AS shoeorder, EXTRACT(DAY FROM tlDate) as pdate
  FROM tblshoes
  WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
  GROUP BY EXTRACT(DAY FROM tlDate)
  ) a

left join (
  SELECT COUNT(*) AS pantorder, EXTRACT(DAY FROM tlDate) as pdate
  FROM tblpants
  WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
  GROUP BY EXTRACT(DAY FROM tlDate)
  ) b
on a.pdate = b.pdate

union

select
   coalesce(a.shoeorder, 0) as shoeorder
  ,coalesce(a.pdate, b.pdate) as pdate
  ,coalesce(b.pantorder, 0) as pantorder
from (
  SELECT COUNT(*) AS shoeorder, EXTRACT(DAY FROM tlDate) as pdate
  FROM tblshoes
  WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
  GROUP BY EXTRACT(DAY FROM tlDate)
  ) a

right join (
  SELECT COUNT(*) AS pantorder, EXTRACT(DAY FROM tlDate) as pdate
  FROM tblpants
  WHERE tlDate >= CURRENT_DATE - INTERVAL 1 MONTH
  GROUP BY EXTRACT(DAY FROM tlDate)
  ) b
on a.pdate = b.pdate

计算所有记录，包括没有值的行和两个表

2 个答案: