MySQL recursive selection from one table - mysql

Question

I have this table in MySQL:
| id | mainid | name |
+----+--------+---------------------+
| 1 | 0 | main 1 |
| 2 | 1 | sub 1 |
| 3 | 1 | sub 2 |
| 4 | 1 | sub 3 |
| 5 | 4 | subsub 1 |
| 6 | 4 | subsub 2 |
| 7 | 0 | main 2 |
| 8 | 7 | sub 4 |
| 9 | 7 | sub 5 |
The mainid field is associate with id field.
Is there a best practice in MySQL commands to select all row recursive? I want to select all subitems under main item.
I tried to select all subitems on first level for example sub 1, sub 2, sub3 is under main 1. This is simple:
SELECT id, mainid, name FROM mytable WHERE mainid = '1';
But is there a one-line-command to select same rows AND the subsub1 and subsub 2 rows too? (And of cours if I create another deeper levels thats too.)

Answer 1

you'll need temp tables and separate stored procedures
first stored procedure will receive the "parent" id and create a result temp table:
RESULT (id, mainid, name)
and a check temp table
CHECK (id, passed)
(this table is necessary to avoid infinite loops)
So, the idea is that you call the inner stored procedure, and the inner stored is something like this
PROC (currentId (int))
with the parent id and the proc will do basically what your query did, but save it in a inner temp table, and then for each element of that temp table (that is not in CHECK) it will mark it as passed in CHECK (just insert the row) and call the same proc for each of the "children" of currentId
Then insert all data from the inner temp table into RESULT and you'll have your entire list of descendants
you have 2 ways
check children and then insert into RESULT
or
insert into RESULT and then check children
the data will be ordered differently but the result should be the same