SQL 如何针对给定范围对列进行分组并加入其他 table 以计算与第一列相关的行

Question

我需要根据给定的年份范围对用户列进行分组。这是示例年份范围 (1980-1989,1990-1999,2000-2009) 然后，我需要加入计算另一个 table 的结果。我创建了一个数据库 "user_relations" 并创建了两个 table 来显示我的问题。

+--------------------------+
| Tables_in_user_relations |
+--------------------------+
| user_answers             |
| users                    |
+--------------------------+
2 rows in set (0.00 sec)

这是用户 table

+----+----------+-----------+
| id | username | birthyear |
+----+----------+-----------+
|  1 | user1    |      1980 |
|  2 | user2    |      1990 |
|  3 | user3    |      2000 |
|  4 | user4    |      1983 |
+----+----------+-----------+
4 rows in set (0.00 sec)

这是 user_answers table。我只需要根据按日期范围分组的用户数 user_answers。

+----+---------+-----------+
| id | user_id | option_id |
+----+---------+-----------+
|  1 |       1 |         1 |
|  2 |       2 |         1 |
|  3 |       3 |         2 |
|  4 |       4 |         1 |
+----+---------+-----------+
4 rows in set (0.00 sec)

根据这些 tables，我需要得到这样的结果。

+------------------------------------------------
| option_id | 1980-1989 | 1990-1999 | 2000-2009 |
+------------------------------------------------
|  1        |         2 |         1 |         0 |
|  2        |         0 |         0 |         1 |
|  3        |         0 |         0 |         0 |
+------------------------------------------------

注意：我需要先使用用户table。我知道可能会有很多变化来获得这个结果。但是我必须以这种方式得到结果。这只是一个例子。

我希望那边有人能帮助我。谢谢。

Answer 1

为此，您可以在求和中使用 case 语句，相当简单：

select ua.option_id,
       sum(case when u.birthyear between 1980 and 1989 then 1 else 0 end) as "1980-1989",
       sum(case when u.birthyear between 1990 and 1999 then 1 else 0 end) as "1990-1999",
       sum(case when u.birthyear between 2000 and 2009 then 1 else 0 end) as "2000-2009"
from   users as u
inner  join user_answers as ua
on     ua.user_id = u.id
group  by ua.option_id

Answer 2

您可以使用 PIVOT 来执行此操作，大致如下：

SELECT  * from
   (SELECT option_id, 
           CASE  
                WHEN birthyear <= 2009 and birthyear >= 2000 THEN '2000-2009'
                WHEN birthyear <= 1999 and birthyear >= 1990 THEN '1990-1999'
                WHEN birthyear <= 1989 and birthyear >= 1980 THEN '1980-1989' 
--                [.... etc etc]
           END as ranges,
           1 as Responses
    FROM users u 
    INNER JOIN user_answers ua on u.id = ua.userid) source
    PIVOT (sum(responses) for ranges in ([2000-2009], [1990-1999],[1980-1989])) as Pivot

SQL 如何针对给定范围对列进行分组并加入其他 table 以计算与第一列相关的行

SQL How to group a column for a given range and join to other table for counting related rows with the first column

mysql

sql

postgresql

table-relationships