Question

请有人看看这个CTE并告诉我它有什么问题吗？它只返回第一行（锚点）。

修改这应该工作，但我想知道表和数据有什么问题!!!

Create table Menus (MenuID uniqueidentifier primary key, MenuName nvarchar(100))
Create table MenuItems (MenuItemID uniqueidentifier primary key, PID uniqueidentifier null, MenuID uniqueidentifier not null, MenuItemName nvarchar(100) not null)

insert into Menus values ('3AB564A7-1D2C-4C43-91E3-A191016CBE67', 'Main')

insert into MenuItems values ('D3B92D1B-7AFA-4E11-AF01-9F6A00B1B2A9', '00000000-0000-0000-0000-000000000000', '3AB564A7-1D2C-4C43-91E3-A191016CBE67', 'Books')
insert into MenuItems values ('70575C44-1EF8-497F-B7B8-A18300F645D7', '00000000-0000-0000-0000-000000000000', '3AB564A7-1D2C-4C43-91E3-A191016CBE67', 'CDs')
insert into MenuItems values ('2D6ED5B3-4C6A-4907-8571-A196009727D7', '00000000-0000-0000-0000-000000000000', '3AB564A7-1D2C-4C43-91E3-A191016CBE67', 'DVDs')
insert into MenuItems values ('3A1096E7-5FD2-4F77-9729-A19600973BDF', '2D6ED5B3-4C6A-4907-8571-A196009727D7', '3AB564A7-1D2C-4C43-91E3-A191016CBE67', 'Movies')
insert into MenuItems values ('5C2AC1F8-DEE0-448B-B538-A19600F0839B', '00000000-0000-0000-0000-000000000000', '3AB564A7-1D2C-4C43-91E3-A191016CBE67', 'Cassetes')
GO

declare @MenuID uniqueidentifier
set @MenuID = '3AB564A7-1D2C-4C43-91E3-A191016CBE67'
;WITH 
cte (MenuItemID, PID, Lvl) 
AS 
    (
    select MenuID as MenuItemID, cast(null as uniqueidentifier) as PID, 1
        from Menus where MenuID = @MenuID
    union all
    select MenuItems.MenuItemID
            , PID = case MenuItems.pid when '00000000-0000-0000-0000-000000000000' then @MenuID else MenuItems.pid end
            , cte.Lvl + 1 
        from MenuItems
            inner join cte on cte.MenuItemID = MenuItems.PID
        where MenuItems.MenuID = @MenuID
    )
select * from cte

修改：结果应该是这样的：

3AB564A7-1D2C-4C43-91E3-A191016CBE67    NULL    1
D3B92D1B-7AFA-4E11-AF01-9F6A00B1B2A9    3AB564A7-1D2C-4C43-91E3-A191016CBE67    2
70575C44-1EF8-497F-B7B8-A18300F645D7    3AB564A7-1D2C-4C43-91E3-A191016CBE67    2
2D6ED5B3-4C6A-4907-8571-A196009727D7    3AB564A7-1D2C-4C43-91E3-A191016CBE67    2
5C2AC1F8-DEE0-448B-B538-A19600F0839B    3AB564A7-1D2C-4C43-91E3-A191016CBE67    2
3A1096E7-5FD2-4F77-9729-A19600973BDF    2D6ED5B3-4C6A-4907-8571-A196009727D7    3

提前致谢！

Kardo

Answer 1

问题似乎在

 inner join cte on cte.MenuItemID = MenuItems.PID

因为MenuItemID和PID不匹配。

提供表格结构和样本数据以供进一步分析并实际模拟问题。

Answer 2

最后我使用子查询解决了我的问题：

declare @MenuID uniqueidentifier
set @MenuID = '3AB564A7-1D2C-4C43-91E3-A191016CBE67'
;WITH 
cte (MenuItemID, PID, Lvl) 
AS 
    (
    select MenuID as MenuItemID, cast(null as uniqueidentifier) as PID, 1
        from Menus where MenuID = @MenuID
    union all 
    select mi.MenuItemID, mi.PID, cte.Lvl + 1  from (select MenuItems.MenuItemID
            , PID = case MenuItems.pid when '00000000-0000-0000-0000-000000000000' then @MenuID else MenuItems.pid end
        from MenuItems
        where MenuItems.MenuID = @MenuID) as mi
            inner join cte on cte.MenuItemID = mi.PID
    )
select * from cte

感谢很多人试图帮助我:)。

为什么cte recursive只返回第一行？

2 个答案: