我正在尝试从现有关系表（ PostgreSQL ）中创建父子关系（邻接列表）。
这是现有的关系样本数据
+---------+-----------+-----------+--------+------------+
| Country | State | City | Zip | Population |
+---------+-----------+-----------+--------+------------+
| India | Karnataka | Bengaluru | 560098 | 100 |
| India | Karnataka | Bengaluru | 560019 | 50 |
| India | Karnataka | Bengaluru | 560067 | 50 |
| India | Kerala | Cochin | 690513 | 70 |
| India | Kerala | Cochin | 680213 | 30 |
| India | Andhra | | | 80 |
| India | Kerala | Kannur | | 20 |
+---------+-----------+-----------+--------+------------+
预期输出（邻接表）
+-----+-----+-----------+--------------+------------+
| cid | pid | Name | relationship | Population |
+-----+-----+-----------+--------------+------------+
| 1 | | India | Country | 300 |
| 2 | 1 | Karnataka | State | 100 |
| 3 | 2 | Bengaluru | City | 50 |
| 4 | 3 | 560098 | Zip | 25 |
| 5 | 1 | Karnataka | State | 100 |
| 6 | 2 | Bengaluru | City | 25 |
| 7 | 3 | 560019 | Zip | 20 |
| 8 | 1 | Karnataka | State | 100 |
| 9 | 2 | Bengaluru | City | 25 |
| 10 | 3 | 560067 | Zip | 40 |
| 11 | 1 | Kerala | State | 100 |
| 12 | 4 | Cochin | City | 50 |
| 13 | 5 | 690513 | Zip | 20 |
| 14 | 1 | Kerala | State | 100 |
| 15 | 4 | Cochin | City | 70 |
| 16 | 5 | 680213 | Zip | 30 |
| 17 | 1 | Andhra | State | 100 |
| 18 | 1 | Kerala | State | 100 |
| 19 | 4 | Kannur | City | 50 |
+-----+-----+-----------+--------------+------------+
在如何通过SQL将现有关系表数据转换为邻接表方面，请有人帮我。这样，我们就可以以层次结构格式显示数据。