CTE 进入无限循环？

Question

我有一个这样的table结构

我想在 if(text_id = new_text_id) 之前重复出现的地方。因此，假设我使用 CTE 将 1 作为 text_id 传递给 return 5 作为 text_id。

我试过了，但它进入了无限循环，仍然尝试了 maxrecursion

WITH textHierarchy AS (
    SELECT tm.text_id
    FROM text_master tm 
    WHERE tm.text_id = 1

    UNION ALL

    SELECT tm.text_id
    FROM text_master as tm
    JOIN textHierarchy AS txtHr ON tm.text_id = txtHr.new_text_id -- Terminating Condition
    WHERE txtHr.new_text_id IS NOT NULL 

)
SELECT * FROM textHierarchy option (maxrecursion 5);

请告诉我我做错了什么。

我的目标是在数据库函数中使用此 CTE，并从 Java 调用该函数。

并且可以在函数内部使用 CTE。如果有怎么办？

Answer 1

你说的终止条件不是那个。这是一个连接条件，它定义了当前迭代与下一个迭代之间的关系。

我想你想要：

WITH textHierarchy AS (
    SELECT tm.text_id
    FROM text_master tm 
    WHERE tm.text_id = 1

    UNION ALL

    SELECT tm.text_id
    FROM text_master as tm
    JOIN textHierarchy AS txtHr ON tm.text_id = txtHr.new_text_id 
    WHERE txtHr.text_id <> txtHr.new_text_id -- Termination condition

)
SELECT * FROM textHierarchy option (maxrecursion 5);

Answer 2

你能试试下面的查询吗？我通过了 text_id=1

;WITH Numbers(text_id) AS
(
    SELECT text_id
    from rectab
    where text_id=1
    UNION ALL
    SELECT text_id
    FROM rectab
    WHERE text_id=new_text_id
)
SELECT text_id
FROM Numbers;

Answer 3

create table dbo.text_master_test
(
text_id int,
text_details nvarchar(max),
new_text_id int
)
go

insert into text_master_test
values(1, 'det 1',2), (2, 'det 2',3), (3, 'det 3',4), (4, 'det 4',5), (5, 'det 5',5);
go


WITH textHierarchy AS (
    SELECT tm.text_id, tm.new_text_id, nullif(tm.new_text_id, tm.text_id) as next_text_id
    FROM text_master_test tm 
    WHERE tm.text_id = 1
    UNION ALL
    SELECT tm.text_id, tm.new_text_id, nullif(tm.new_text_id, tm.text_id) as next_text_id
    FROM text_master_test as tm
    JOIN textHierarchy AS txtHr ON tm.text_id = txtHr.next_text_id 

)
SELECT * FROM textHierarchy;
go


create function dbo.textrecursion(@start_text_id int)
returns table
as
return
(
WITH textHierarchy 
AS 
(
    SELECT tm.text_id, tm.text_details, tm.new_text_id, 
        nullif(tm.new_text_id, tm.text_id) as next_text_id
    FROM dbo.text_master_test tm 
    WHERE tm.text_id = @start_text_id
    UNION ALL
    SELECT tm.text_id, tm.text_details, tm.new_text_id,
        nullif(tm.new_text_id, tm.text_id) as next_text_id
    FROM dbo.text_master_test as tm
    JOIN textHierarchy AS txtHr ON tm.text_id = txtHr.next_text_id 
)
select text_id, text_details, new_text_id
from textHierarchy
);
go

select *
from dbo.textrecursion(1)

select *
from dbo.textrecursion(4)

select *
from dbo.textrecursion(5)
go

drop function dbo.textrecursion;
go
drop table dbo.text_master_test
go

CTE 进入无限循环？

CTE goes in infinite loop?

sql

tsql

sql-server

recursive-query

sql-function