如何在 MySQL 右连接中对结果进行排序？

Question

我正在尝试使用以下两个表使用 MySQL 获取全年的月度数据，

1. 贷款
2. 月

贷款

` +--------+--------+-------+----------+
| idloan | amount | tot   | interest |
+--------+--------+-------+----------+
|      3 |  10000 | 15000 |       50 |
|      4 |   5000 |  6000 |       10 |
|      5 |  20000 | 30000 |       10 |
|      6 |  30000 |  3000 |       10 |
|      7 |  15000 | 16500 |       10 |
+--------+--------+-------+----------+ `

月

`+---------+-------+
| idmonth | month |
+---------+-------+
|       1 | 1     |
|       2 | 2     |
|       3 | 3     |
|       4 | 4     |
|       5 | 5     |
|       6 | 6     |
|       7 | 7     |
|       8 | 8     |
|       9 | 9     |
|      10 | 10    |
|      11 | 11    |
|      12 | 12    |
+---------+-------+ `

我使用这个查询来获取空闲贷款的数量、金额总和和每个月的总和，

` SELECT
  m.month,
  COUNT(l.idloan)AS m_count,
  COALESCE(SUM(l.amount),0)AS amount,
  COALESCE(SUM(l.total),0)AS total
  FROM loan l RIGHT JOIN month m using(month)
GROUP BY m.month `

输出是

` +-------+---------+--------+-------+
| month | m_count | amount | total |
+-------+---------+--------+-------+
| 1     |       0 |      0 |     0 |
| 10    |       1 |  15000 | 16500 |
| 11    |       1 |  30000 |  3000 |
| 12    |       3 |  35000 | 51000 |
| 2     |       0 |      0 |     0 |
| 3     |       0 |      0 |     0 |
| 4     |       0 |      0 |     0 |
| 5     |       0 |      0 |     0 |
| 6     |       0 |      0 |     0 |
| 7     |       0 |      0 |     0 |
| 8     |       0 |      0 |     0 |
| 9     |       0 |      0 |     0 |
+-------+---------+--------+-------+ `

我的问题是如何排序以得到这样的输出

` +-------+---------+--------+-------+
| month | m_count | amount | total |
+-------+---------+--------+-------+
| 1     |       0 |      0 |     0 |
| 2     |       0 |      0 |     0 |
| 3     |       0 |      0 |     0 |
| 4     |       0 |      0 |     0 |
| 5     |       0 |      0 |     0 |
| 6     |       0 |      0 |     0 |
| 7     |       0 |      0 |     0 |
| 8     |       0 |      0 |     0 |
| 9     |       0 |      0 |     0 |
| 10    |       1 |  15000 | 16500 |
| 11    |       1 |  30000 |  3000 |
| 12    |       3 |  35000 | 51000 |
+-------+---------+--------+-------+ `

Answer 1

我相信你只需要一个 order by 条款。 所以你的查询应该是

 SELECT
  m.month,
  COUNT(l.idloan)AS m_count,
  COALESCE(SUM(l.amount),0)AS amount,
  COALESCE(SUM(l.total),0)AS total
  FROM loan l RIGHT JOIN month m using(month)
GROUP BY m.month
ORDER BY CONVERT(m.month,UNSIGNED INTEGER)

Answer 2

如果可能，您应该将月表的月列的数据类型更改为 INT。

无论如何，您仍然可以在 order by 子句中将字符串转换/转换为整数。

像下面这样

SELECT m.month, 
COUNT(l.idloan)AS m_count,
COALESCE(SUM(l.amount),0)AS amount, 
COALESCE(SUM(l.total),0)AS total FROM loan l 
RIGHT JOIN month m using(month) GROUP BY m.month 
ORDER BY CONVERT(m.month,UNSIGNED INTEGER)

建议您更改数据类型，而不是在 order by 子句中使用CONVERT 。