CTE goes in infinite loop?

Question

I have a table structure like this

Where I want to recur till if(text_id = new_text_id). So suppose I pass 1 as text_id I want in return 5 as text_id using CTE.

I tried but it goes in infinite loop, tried maxrecursion still

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);

Please tell me what I am doing wrong.

My aim is to use this CTE inside a database function and call that function from Java.

And can a CTE be used inside a function. If so how?

Answer 1

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