SQL 加入 table 有 0 个可用值

Question

我在寻找正确的联接以从我的 table 获取预期输出时遇到了一些麻烦。我的数据集存在于不同的 table 中：

客户table

+-----------+------------+------------+-------------+--------+
| Client_No | Start_Date |   End_Date | YearOfBirth |  City  |
+-----------+------------+------------+-------------+--------+
|     1     |  1-1-2018  |    null    |    1962     |    A   |
+-----------+------------+------------+-------------+--------+
|     2     |  10-4-2016 |    null    |    1987     |    B   |
+-----------+------------+------------+-------------+--------+
|     3     | 31-12-2015 |    null    |    1992     |    A   |
+-----------+------------+------------+-------------+--------+
|     4     |  1-4-2019  | 31-12-2019 |    2001     |    B   |
+-----------+------------+------------+-------------+--------+
|     5     |  1-1-2018  |    null    |    1999     |    A   |
+-----------+------------+------------+-------------+--------+

日历table

+-----------+
|   Date    |
+-----------+
| 1-1-2019  |
+-----------+
| 1-2-2019  |
+-----------+
| 1-3-2019  |
+-----------+
| 1-4-2019  |
+-----------+
| ........  |
+-----------+
| 1-12-2020 |
+-----------+

出生年份table

+--------+
|  Year  |
+--------+
|  1910  |
+--------+
|  1911  |
+--------+
|  ....  |
+--------+
|  2020  |
+--------+

我想要的是 table 每个城市的人口数量，按 YearOfBirth 统计。但我希望它在我的日历中的每个日期都重新计算。如果 YearOfBirth 为 0，它还必须显示金额。到目前为止我得到的查询：

SELECT a.City, a.YearOfBirth, c.Date, 
       (SELECT COUNT(DISTINCT(b.ClientNo))
        FROM Client as b
        WHERE b.Start_Date < c.Date
        AND (b.End_Date > c.Date OR b.End_Date is null)
        AND a.City = b.City
        AND a.YearOfBirth = b.YearOfBirth) as Amount
FROM Client as a
FULL OUTER JOIN Calender as c
ON a.Start_Date <= c.Date
AND b.Start_Date >= c.Date
FULL OUTER JOIN YearOfBirth as d
ON a.YearOfBirth = d.YearOfBirth
GROUP BY a.City, a.YearOfBirth, c.Date

查询工作正常，但我错过了计数为 0 的所有年份。知道如何解决这个问题吗？

预期输出：

+------+----------+-------------+--------+
| City |   Date   | YearOfBirth | Amount |
+------+----------+-------------+--------+
|  A   | 1-1-2019 |    1910     |    0   |
+------+----------+-------------+--------+
|  A   | 1-1-2019 |    1911     |    0   |
+------+----------+-------------+--------+
|  A   | 1-1-2019 |    1912     |    0   |
+------+----------+-------------+--------+
|  A   | 1-1-2019 |    1962     |    1   |
+------+----------+-------------+--------+

我不会把所有的记录都放进去，因为我希望每个城市的每个日期都有一个记录，其中包含特定年份出生的人数，当它为 0 时也是如此。

Answer 1

我会按照下面的方式做。

使用笛卡尔连接获取城市、year_of_birth 和日期的所有可能组合的列表。

之后我只需要根据城市year_of_birth和日期是否匹配开始和结束日期然后分组来将值与clienttable中的条目进行比较。

因此在缺少 clientid 的情况下，它们将被视为 null，显示为 0

with data
  as (select c.city,a.year_of_birth,b.date
        from YearOfBirth a
        join calendar b
          on 1=1
        join (select distinct city
                from clienttable
             )c
          on 1=1 
      )
 select m.city 
       ,m.date
       ,m.year_of_birth
       ,count(clientid) as amount
   from data m
left join clienttable n
     on m.city=n.city
    and m.year_of_birth=n.year_of_birth
    and m.date between n.start_date and isnull(n.end_date,'3000-12-31')
group by m.city 
       ,m.date
       ,m.year_of_birth

SQL 加入 table 有 0 个可用值

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