不止一个加入MYSQL?
我需要找出子菜单根菜单的id 为此,我使用:不止一个加入MYSQL?,mysql,sql,join,Mysql,Sql,Join,我需要找出子菜单根菜单的id 为此,我使用: **Sub Menu** id|title 1 | Sub A **Root_Sub** id|root_id|sub_id 1 |9 |1 **Root Menu** id|title 9 | Root X 这给了我'9'作为ID 但我还需要得到根菜单的标题,即标题“根X”。我该怎么做 SELECT * FROM sub_menu LEFT JOIN root_sub ON sub_menu.id = root_sub.sub_i
**Sub Menu**
id|title
1 | Sub A
**Root_Sub**
id|root_id|sub_id
1 |9 |1
**Root Menu**
id|title
9 | Root X
这给了我'9'作为ID
但我还需要得到根菜单的标题,即标题“根X”。我该怎么做
SELECT * FROM sub_menu LEFT JOIN root_sub ON sub_menu.id = root_sub.sub_id
内部联接
,但如果其中一个可为空,则将内部联接
更改为左联接
SELECT *
FROM sub_menu
LEFT JOIN root_sub ON sub_menu.id = root_sub.sub_id
LEFT JOIN root_menu ON root_sub.root_id = root_menu.id
SELECT a.ID AS subID,
a.title AS SubTitle,
c.ID AS RootID,
c.Title as RootTitle
FROM sub_Menu a
INNER JOIN root_sub b
On a.ID = b.sub_ID
INNER JOIn root_Menu c
ON b.root_ID = c.ID