SQL：按rowID排序，然后根据rowid按列排序答案

【问题标题】：SQL: Order by rowID and then by column based on the rowidSQL：按rowID排序，然后根据rowid按列排序
【发布时间】：2017-07-01 02:51:22
【问题描述】：

我有以下'departments' 表：

+-------+-------------+-------------------+
| rowid | department  | parent_department |
+-------+-------------+-------------------+
| 10    | Main Office | NULL              |
+-------+-------------+-------------------+
| 11    | Back Office | 10                |
+-------+-------------+-------------------+
| 12    | Commercial  | NULL              |
+-------+-------------+-------------------+
| 13    | Outdoor     | NULL              |
+-------+-------------+-------------------+
| 14    | Beach       | 13                |
+-------+-------------+-------------------+
| 15    | Gardening   | 13                |
+-------+-------------+-------------------+
| 16    | Accounting  | 10                |
+-------+-------------+-------------------+

我想根据 rowid 和 parent_department 来订购它：

+-------+-------------+-------------------+
| rowid | department  | parent_department |
+-------+-------------+-------------------+
| 10    | Main Office | NULL              |
+-------+-------------+-------------------+
| 11    | Back Office | 10                |
+-------+-------------+-------------------+
| 16    | Accounting  | 10                |
+-------+-------------+-------------------+
| 13    | Outdoor     | NULL              |
+-------+-------------+-------------------+
| 14    | Beach       | 13                |
+-------+-------------+-------------------+
| 15    | Gardening   | 13                |
+-------+-------------+-------------------+
| 12    | Commercial  | NULL              |
+-------+-------------+-------------------+

这样对于每个rowid，查找'parents_departments' 是否存在并按如下顺序显示。

请注意，我没有设计当前表格，遗憾的是我没有更改它的权限

【问题讨论】：

标签： mysql sql database sorting sql-order-by

【解决方案1】：

试试这个：

SELECT rowid, department, parent_department
  FROM departments
 ORDER BY IFNULL(parent_department, rowid), rowid;

【讨论】：

@shmosel...不错的一个....但是我在我的本地和它的返回 rowid 上按顺序尝试了 10,11,16,12,13,14,15
@AnkitAgrawal 如果父组之间应该有任何排序，OP 没有指定它。我的假设是没关系。