Mysql SELECT查询中的IF和CASE语句及其子查询
如果Mysql SELECT查询中的IF和CASE语句及其子查询,mysql,subquery,inner-join,Mysql,Subquery,Inner Join,如果菜单项,下面的查询返回NULL。父项不是0,这是错误的 我在这里试图做的是,如果菜单项.parent行的值为0,则将其作为原始值返回,但如果值不是0,则返回相应行的名称(varchar),该行的值是什么 你知道我为什么一直是空的吗 注意:所有其他选定列都是正常的,因此查询本身是正常的 谢谢 示例1: SELECT ... ... ( CASE WHEN menu_items.parent = '0' THEN menu_items.parent ELSE (SE
菜单项,下面的查询返回NULL。父项不是0,这是错误的
我在这里试图做的是,如果菜单项.parent
行的值为0,则将其作为原始值返回,但如果值不是0,则返回相应行的名称(varchar),该行的值是什么
你知道我为什么一直是空的吗
注意:所有其他选定列都是正常的,因此查询本身是正常的
谢谢
示例1:
SELECT
...
...
(
CASE
WHEN menu_items.parent = '0' THEN menu_items.parent
ELSE (SELECT name FROM menu_items WHERE id = menu_items.parent)
END
) AS ParentID
...
...
FROM menus
INNER JOIN menu_items ...
...
...
SELECT
...
...
IF
(
menu_items.parent = '0',
menu_items.parent,
(SELECT name FROM menu_items WHERE id = menu_items.parent)
) ParentID
...
...
FROM menus
INNER JOIN menu_items ...
...
...
SELECT
menus.name AS MenuName,
menu_items.id AS MenuItemsId,
menu_items.name AS MenuItemsName
/*
Sub section should go here
*/
FROM users
INNER JOIN assigned_menus ON assigned_menus.fk_users_id = users.id
INNER JOIN menu_items ON menu_items.id = assigned_menus.fk_menu_items_id
INNER JOIN menus ON menus.id = menu_items.fk_menus_id
WHERE
users.id = ? AND
users.is_active = 'YES' AND
menu_items.is_active = 'YES' AND
menus.is_active = 'YES'
ORDER BY
MenuName,
MenuItemsName
示例2:
SELECT
...
...
(
CASE
WHEN menu_items.parent = '0' THEN menu_items.parent
ELSE (SELECT name FROM menu_items WHERE id = menu_items.parent)
END
) AS ParentID
...
...
FROM menus
INNER JOIN menu_items ...
...
...
SELECT
...
...
IF
(
menu_items.parent = '0',
menu_items.parent,
(SELECT name FROM menu_items WHERE id = menu_items.parent)
) ParentID
...
...
FROM menus
INNER JOIN menu_items ...
...
...
SELECT
menus.name AS MenuName,
menu_items.id AS MenuItemsId,
menu_items.name AS MenuItemsName
/*
Sub section should go here
*/
FROM users
INNER JOIN assigned_menus ON assigned_menus.fk_users_id = users.id
INNER JOIN menu_items ON menu_items.id = assigned_menus.fk_menu_items_id
INNER JOIN menus ON menus.id = menu_items.fk_menus_id
WHERE
users.id = ? AND
users.is_active = 'YES' AND
menu_items.is_active = 'YES' AND
menus.is_active = 'YES'
ORDER BY
MenuName,
MenuItemsName
实际查询:
SELECT
...
...
(
CASE
WHEN menu_items.parent = '0' THEN menu_items.parent
ELSE (SELECT name FROM menu_items WHERE id = menu_items.parent)
END
) AS ParentID
...
...
FROM menus
INNER JOIN menu_items ...
...
...
SELECT
...
...
IF
(
menu_items.parent = '0',
menu_items.parent,
(SELECT name FROM menu_items WHERE id = menu_items.parent)
) ParentID
...
...
FROM menus
INNER JOIN menu_items ...
...
...
SELECT
menus.name AS MenuName,
menu_items.id AS MenuItemsId,
menu_items.name AS MenuItemsName
/*
Sub section should go here
*/
FROM users
INNER JOIN assigned_menus ON assigned_menus.fk_users_id = users.id
INNER JOIN menu_items ON menu_items.id = assigned_menus.fk_menu_items_id
INNER JOIN menus ON menus.id = menu_items.fk_menus_id
WHERE
users.id = ? AND
users.is_active = 'YES' AND
menu_items.is_active = 'YES' AND
menus.is_active = 'YES'
ORDER BY
MenuName,
MenuItemsName
菜单项表
ID name parent fk_menu_items_id
1 Menus 0 1
2 Roles 0 1
3 Permissions 0 1
4 Users 0 1
5 Files 0 1
6 File Uploads 0 1
7 University 6 1
8 Details 6 1
9 Progress 6 1
10 Assg 6 1
11 Applications 0 2
12 New 11 2
13 Edit 11 2
14 Rejected 11 2
15 Approved 11 2
16 Exs 0 2
17 Assm 16 2
18 Stf 0 3
19 Std 0 3
20 Prg 19 3
21 Comm 0 4
22 Sms 21 4
23 Sms2 21 4
24 New2 0 4
25 Act 0 4
菜单项。如果菜单项,则名称
不同。父项
不是0
,因此您只返回同一行的名称,而不是编号:)非常感谢。