Question

我有两个表需要联接，并且需要获取可用于绘制的数据。

两个表的样本数据是：

**table1**

month       planned_hours
2019-10-01  24
2020-01-01  67
2019-02-01  12

**table2**
date         hrs_consumed
2019-12-07   7
2019-09-09   3
2019-10-12   4
2019-02-01   5
2019-10-11   4

我尝试了以下查询：

SELECT 
  a.date as month1,
  a.hrs as planned_hours,
  a.mon_hrs as actual_hours 
FROM (
  SELECT 
    sum(t1.hrs_consumed) as hrs,
    t1.date,
    t2.mon_hrs
  FROM booking t1
  LEFT JOIN monthly_plan t2 
  ON month(t1.date) = month(t2.mon)
  UNION
  SELECT 
    t2.mon_hrs,
    t2.mon as date,
    sum(t1.hrs_consumed) as hrs
  FROM booking t1
  RIGHT JOIN monthly_plan t2 
  ON month(t1.date) = month(t2.mon)) a

我从查询中得到以下输出：

month1      planned_hrs  actual_hrs
2019-10-01  24           8
2019-10-01  24           8

我想要得到的输出是：

month1   planned_hrs   actual_hrs
10-2019  24            8
12-2019  0             7
08-2019  0             3
01-2020  67            0
02-2019  12            5

Answer 1

您可以将不同的月份加入表格并进行汇总：

SELECT 
  t.month,
  COALESCE(MAX(t1.planned_hours), 0) planned_hours,
  COALESCE(SUM(hrs_consumed), 0) actual_hrs
FROM (
  SELECT DATE_FORMAT(month, "%m-%Y") month FROM table1
  UNION
  SELECT DATE_FORMAT(date, "%m-%Y") FROM table2
) t
LEFT JOIN table1 t1 ON t.month = DATE_FORMAT(t1.month, "%m-%Y")
LEFT JOIN table2 t2 ON t.month = DATE_FORMAT(t2.date, "%m-%Y")
GROUP BY t.month

请参见demo。
结果：

| month   | planned_hours | actual_hrs |
| ------- | ------------- | ---------- |
| 01-2020 | 67            | 0          |
| 02-2019 | 12            | 5          |
| 09-2019 | 0             | 3          |
| 10-2019 | 24            | 8          |
| 12-2019 | 0             | 7          |

在日期联接两个表

1 个答案: