SQL Delete Where Not In with Composite Key - sql

Question

I have a system integration project which needs to CRUD from one DB to another. Not especially complicated. However, when it comes to deleting rows which exist in the target but not in the source, I ran into a little trouble. The standard patterns include: LEFT JOIN, NOT EXISTS or NOT IN. I chose the LEFT JOIN. My 'Phone' table uses a composite key, Employee 'Id' and the PhoneType: Work, Home, Mobile, etc. The standard left join will delete ANY target Phone number NOT in the source. This clears out the whole table. NOTE: I am updating only records which have changed since the last update, NOT the whole target & source. So, I wrote a fix which I suspect is really poor SQL:
-- SOURCE
DECLARE #tmpPhones TABLE(Id varchar(8), PhoneType int, PhoneNumber varchar(30), PRIMARY KEY (Id, PhoneType))
INSERT into #tmpPhones values
('TEST123', 1, '12345678'),
('TEST123', 2, '12345678'),
('TEST123', 3, '12345678')
-- TARGET
DECLARE#Phone TABLE( Id varchar(8), PhoneType int, PhoneNumber varchar(30), PRIMARY KEY (Id, PhoneType))
INSERT into #Phone values
('TEST123', 1, '12345678'), <-- Exists in both, leave
('TEST123', 2, '12345678'), <-- Exists in both, leave
('TEST123', 3, '12345678'), <-- Exists in both, leave
('TEST123', 4, '12345678'), <-- ONLY delete this one!
('TEST456', 2, '12345678'), <-- Ignore this employee Id
('TEST456', 3, '12345678'), ""
('TEST456', 4, '12345678') ""
DELETE p
FROM #Phone p
LEFT JOIN #tmpPhones t
ON t.Id = p.Id AND t.PhoneType = p.PhoneType
WHERE t.Id IS NULL AND t.PhoneType IS NULL
AND p.Id IN (SELECT Id FROM #tmpPhones) <-- a sad hack?
This works, but I feel like there is a better way to make sure we are only deleting records for THIS employee, not all the others.
Any suggestions?

Answer 1

Use exists.
DELETE p
FROM #Phone p
where exists (select 1 from #tmpPhones where Id = p.Id)
AND not exists (select 1 from #tmpPhones where PhoneType = p.PhoneType)
Edit: Deleting using cte.
with todelete as (
select id,phonetype from phone
except
select id,phonetype from tmpphones t
where exists (select 1 from phone where id = t.id)
)
delete from phone
where exists (select 1 from todelete where phone.id = id and phone.phonetype = phonetype)

Answer 2

I think two exists statements pretty much capture the logic: as you describe it
DELETE p
FROM #Phone p
WHERE EXISTS (SELECT 1 FROM #tmpPhone t WHERE t.id = p.id) AND
NOT EXISTS (SELECT 1 FROM #tmpPhone t WHERE t.id = p.id AND t.PhoneType = p.PhoneType) ;

Answer 3

merge seems to work ok - but you still need to see if the id is in your reference set, I don't see a clean way around that
MERGE #Phone AS TGT
USING (
SELECT * FROM #tmpPhones
) AS SRC
ON TGT.ID=SRC.ID AND TGT.PHONETYPE=SRC.PHONETYPE
WHEN NOT MATCHED BY SOURCE AND tgt.id IN (SELECT id FROM #tmpPhones) THEN DELETE;