MySQL - 单句实现无限层次父子关系查询

CREATE TABLE table1(id int, name varchar(10), parent_id int);
INSERT table1 VALUES
(1, ‘Home’, 0),
(2, ‘About’, 1),
(3, ‘Contact’, 1),
(4, ‘Legal’, 2),
(5, ‘Privacy’, 4),
(6, ‘Products’, 1),
(7, ‘Support’, 2);

SELECT ID.level, DATA.* FROM(
SELECT
@id as _id,
( SELECT @id := parent_id
FROM table1
WHERE id = @id
) as _pid,
@l := @l+1 as level
FROM table1,
(SELECT @id := 5, @l := 0 ) b
WHERE @id > 0
) ID, table1 DATA
WHERE ID._id = DATA.id
ORDER BY level;

SELECT ID.level, DATA.* FROM(
SELECT
@ids as _ids,
( SELECT @ids := GROUP_CONCAT(id)
FROM table1
WHERE FIND_IN_SET(parent_id, @ids)
) as cids,
@l := @l+1 as level
FROM table1,
(SELECT @ids :=’1’, @l := 0 ) b
WHERE @ids IS NOT NULL
) id, table1 DATA
WHERE FIND_IN_SET(DATA.id, ID._ids)
ORDER BY level, id