MySQL recursive 递归

MySQL 从最内的select开始执行，但是同一个select clause可以在查询的结果上继续查询。

SELECT menu_id,parent_id,(SELECT m1.parent_id FROM sys_menu AS m1 WHERE m1.menu_id=m.parent_id) FROM sys_menu AS m WHERE m.menu_id = 89

方案1.通过recursive递归

使用MySQL的CTE 方法，通过子节点向上查询

SELECT DISTINCT *  FROM (	
WITH recursive recur_menu_nodes_child AS (SELECTm.* FROMsys_menu AS m,sys_user AS u,sys_role AS r,sys_role_menu AS rm WHEREu.user_role = r.role_id AND r.role_id = rm.role_id AND m.menu_id = rm.menu_id AND u.user_id = 1UNION ALLSELECT n.* FROM sys_menu AS n JOIN recur_menu_nodes_child pn ON pn.parent_id = n.menu_id
)SELECT * FROM recur_menu_nodes_child
) AS tab

通过UNION DISTINCT简化后

WITH recursive recur_menu_nodes_child AS (SELECTm.* FROMsys_menu AS m,sys_user AS u,sys_role AS r,sys_role_menu AS rm WHEREu.user_role = r.role_id AND r.role_id = rm.role_id AND m.menu_id = rm.menu_id AND u.user_id = 247 UNION DISTINCTSELECT n.* FROM sys_menu AS n JOIN recur_menu_nodes_child pn ON pn.parent_id = n.menu_id
)SELECT * FROM recur_menu_nodes_child

方案2. 通过变量赋值

只适用于一个节点，而不是多个节点。

SELECTd3.* 
FROM(SELECT@r AS id,( SELECT @r := parent_id FROM sys_menu WHERE menu_id = @r ) AS parent_id FROM( SELECT @r := 89 ) child,sys_menu hd) d2INNER JOIN sys_menu d3 ON d2.id = d3.menu_id 
ORDER BYd3.menu_id

或者

更简单点

SELECT m.* FROM sys_menu AS m,(
SELECT @r AS _id,(SELECT @r := parent_id FROM sys_menu WHERE menu_id = _id) AS parent_idFROM(SELECT @r := 89) vars, sys_menu AS hWHERE @r <> 0 
) AS tab WHERE m.menu_id = tab._id