MySql: ORDER BY parent and child

Question

I have a table like:

+------+---------+-
| id   | parent  |
+------+---------+
| 2043 |    NULL |
| 2044 |    2043 |
| 2045 |    2043 |
| 2049 |    2043 |
|          


        

Answer 1

If your table uses 0 instead of null to indicate an entry with no parent:

id   | parent
-------------
1233 | 0
1234 | 1233
1235 | 0
1236 | 1233
1237 | 1235

Use greatest instead of coalesce and check the value does not equal 0:

ORDER BY GREATEST(parent, id), parent != 0, id