Mysql选择以查看层次结构

Question

I am developing a way to store files using php & mysql. I am hitting a "mind freeze" with this piece of SQL

So, i have this table:

IDIGORDISKFOLDER   NAME       PARENT
1                  |/             |(null)
6                  |subfolderl2   |2
3                  |/             |(null)
4                  |pics          |1
5                  |/             |0
6                  |subfolderl2   |2
7                  |subfolderl3   |6

And I am trying to get Something like this: getting parents for id number 7

IDIGORDISKFOLDER   NAME       PARENT
7                  |subfolder13   |6
6                  |subfolderl2   |2
6                  |subfolderl2   |2
1                  |/             |(null)

After some extensive search, I've created the following (SQL) code:

DROP PROCEDURE IF EXISTS getTopParents;
delimiter //
DROP PROCEDURE IF EXISTS getTopParents;
CREATE PROCEDURE getTopParents(in someId int)
BEGIN
declare pid int default NULL;
SELECT parent into pid from igorDiskFolder WHERE idigorDiskFolder = someId;
    if (pid is not NULL) then
        select idigorDiskFolder, name, parent from igorDiskFolder where idigorDiskFolder = someId;
        CALL getTopParents(pid);
    end if;
END //
delimiter ;

call getTopParents(2);

But, for some reason, I can't get it running. The SELECT statements itself are working. the "declare" seems to throw an error. I've also tried with SET @pid, but with no luck. If it helps, look at this non-working fiddle: http://sqlfiddle.com/#!2/e3cc6/2

Also, I'd be willing to do this via PHP & MySQL(i), but I don't know if it will affect performance.

Answer 1

A fairly standard approach is using @var to keep track of parent:

select idigorDiskFolder, name, @id := parent parent
from (select * from igorDiskFolder order by parent desc) a
join (select @id := 7) b
where idigorDiskFolder = @id;

fiddle