Get related rows from SQL Server - sql

Question

I have just one SQL query that I want help for.
As you can see below, there are 4 emails. 3 of the 4 messages are related (15482, 15483 and 15484). I would like to have these rows out.
You can relate them to each other through column messageid = ReplyTo and ReplyTo = MessageID. It ends up being recrusiv.
The picture below shows what I have right now, but as I said I only want the ID 15482, 15483 and 15484 shown and not 15485. Because as you can see, the first 3 rows is an email thread that hangs together while the last is a new mail
How can I do that, when I only know ID 15482
This is my SQL statement
select
t1.id, t1.From_, t1.MessageId, t2.ReplyTo
from
HelpDesk_Z01_Emails as t1
left join
HelpDesk_Z01_EmailsReplyTo as t2 on t1.MessageId = t2.MessageId
This is my output:

Answer 1

You correctly said that it is a recursion.
Usually it is done using recursive common table expression
I'm not sure if everything in the query below is correct. If you had provided a simplified example with sample data it would be possible to try the suggested solution. Without it, the query is written, but not tested. Give it a try.
WITH
CTE
AS
(
SELECT
t1.id, t1.From_, t1.MessageId, t2.ReplyTo
FROM
HelpDesk_Z01_Emails as t1
left join HelpDesk_Z01_EmailsReplyTo as t2 on t1.MessageId = t2.MessageId
WHERE t1.id = 15482
UNION ALL
SELECT
t1.id, t1.From_, t1.MessageId, t2.ReplyTo
FROM
HelpDesk_Z01_Emails as t1
left join HelpDesk_Z01_EmailsReplyTo as t2 on t1.MessageId = t2.MessageId
INNER JOIN CTE ON CTE.MessageId = t2.ReplyTo
)
SELECT *
FROM CTE
;
This is the script to make a simplified table with sample data that you should have included in your question:
DECLARE #T TABLE(id int, From_ varchar(255), MessageId varchar(255), ReplyTo varchar(255));
INSERT INTO #T (id, From_, MessageId, ReplyTo) VALUES (15482, 'test#com', 'CAF', NULL);
INSERT INTO #T (id, From_, MessageId, ReplyTo) VALUES (15483, 'test#com', '54c', 'CAF');
INSERT INTO #T (id, From_, MessageId, ReplyTo) VALUES (15484, 'test#com', 'Fk', '54c');
INSERT INTO #T (id, From_, MessageId, ReplyTo) VALUES (15485, 'test#com', 'FkMh', NULL);
Having such starting point it is easy to write and verify the following query:
WITH
CTE
AS
(
SELECT
TT.id, TT.From_, TT.MessageId, TT.ReplyTo
FROM
#T AS TT
WHERE TT.id = 15482
UNION ALL
SELECT
TT.id, TT.From_, TT.MessageId, TT.ReplyTo
FROM
#T AS TT
INNER JOIN CTE ON CTE.MessageId = TT.ReplyTo
)
SELECT *
FROM CTE
;
The result set:
id From_ MessageId ReplyTo
15482 test#com CAF NULL
15483 test#com 54c CAF
15484 test#com Fk 54c