+-------------+------+
| 列名 | 类型 |
+-------------+------+
| account_id | int |
| income | int |
+-------------+------+
account_id 是这个表的主键。
每一行都包含一个银行帐户的月收入的信息。
Accounts 表:
+------------+--------+
| account_id | income |
+------------+--------+
| 3 | 108939 |
| 2 | 12747 |
| 8 | 87709 |
| 6 | 91796 |
+------------+--------+
Result 表:
+----------------+----------------+
| category | accounts_count |
+----------------+----------------+
| Low Salary | 1 |
| Average Salary | 0 |
| High Salary | 3 |
+----------------+----------------+
低薪: 数量为 2.
中等薪水: 没有.
高薪: 有三个账户,他们是 3, 6和 8.
SELECT 'Low Salary' category,sum(if(income<20000,1,0)) accounts_count FROM accounts
UNION
SELECT 'Average Salary' category,sum(if(income between 20000 and 50000,1,0)) accounts_count FROM accounts
UNION
SELECT 'High Salary' category,sum(if(income>50000,1,0)) accounts_count FROM accounts