SQL:按rowID排序，然后根据rowid按列进行排序

Question

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                |
+-------+-------------+-------------------+

我想以rowid和parent_department为基础订购如下：

+-------+-------------+-------------------+
| 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              |
+-------+-------------+-------------------+

因此，对于每个rowid，查找'parents_departments'是否存在，并按以下方式显示顺序。

请注意，我没有设计当前的表，遗憾的是，我没有更改它的权限。

Answer 1

试试这个：

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