sqlserver 公共表达式小体验

创建测试数据表

CREATE TABLE [dbo].[test](
[id] [int] IDENTITY(1,1) NOT NULL,
[parent_id] [int] NULL,
[agent] [bit] NULL,
CONSTRAINT [PK_test] PRIMARY KEY CLUSTERED
(
[id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (1, 0, 1)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (2, 1, 0)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (3, 1, 1)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (4, 2, 0)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (5, 3, 1)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (6, 3, 0)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (7, 6, 0)
GO
INSERT [dbo].[test] ([id], [parent_id], [agent]) VALUES (8, 1, 0)
GO

通过公共表达式查找想要的数据

with test_CTE
as (
select *,10 as tlevel from test where id = 7
union all
select t.*,cte.tlevel-1 from test as t
inner join test_CTE as cte on t.id = cte.parent_id
)

select top 1 * from test_CTE
where agent=1
order by tlevel Desc