SQL：按行ID排序，然后根据rowid

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

我想根据rowid和parent_department这样订购它：

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

因此，对于每个 rowid ，查找是否存在'parents_departments'并按以下顺序显示。

请注意，我没有设计当前的表格，遗憾的是我没有更改权限

Answer 1

试试这个：

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