按列值按LIKE分组

Question

给定这样的假设查询：

SELECT COUNT(*)
FROM subscriptions
GROUP by plan_type

并有一个类似于下面的表格：

+----+-----------------------+-------------+--+
| id |       plan_type       | customer_id |  |
+----+-----------------------+-------------+--+
|  1 | gold_2017             |         523 |  |
|  2 | gold_2016_recurring   |        2300 |  |
|  3 | silver_2016           |         234 |  |
|  4 | silver_2017_recurring |        2593 |  |
|  5 | platinum_recurring    |        4123 |  |
+----+-----------------------+-------------+--+

所需结果：

+-------+----------+
| count |   type   |
+-------+----------+
|     2 | gold     |
|     2 | silver   |
|     1 | platinum |
+-------+----------+

有什么方法可以使用GROUP BY和LIKE语句（LIKE“ silver”，LIKE“ gold”，LIKE“ platinum”等）对这些条目进行分组？

Answer 1

您可以使用case：

SELECT (CASE WHEN plan_type LIKE 'silver%' THEN 'silver'
             WHEN plan_type LIKE 'gold%' THEN 'gold'
             WHEN plan_type LIKE 'platinum%' THEN 'platinum'
        END) as plan_grp, COUNT(*)
FROM subscriptions
GROUP by (CASE WHEN plan_type LIKE 'silver%' THEN 'silver'
               WHEN plan_type LIKE 'gold%' THEN 'gold'
               WHEN plan_type LIKE 'platinum%' THEN 'platinum'
          END);

某些数据库允许您在中使用列别名GROUP BY。