Search for records that do not contain a specific value

Question

I have a table that contains IDs from two other tables. Those are two integer numbers.

CustomerId  SectionId
====================
1           1
1           2
1           3
2           2
2           3
3           1
3           2
3           3
4           2
4           3

What I am looking for is for those records that have the SectionId=1 missing. For the above example I need to retrieve CustomerId 2 and 4.

I cannot do a Select customer ID where SectionId <> 1 because it will bring me all records (1 to 4). I specifically need those that, independently of which SectionId they have, are missing SectionId=1

Thanks.

Answer 1

You need NOT EXISTS :

SELECT DISTINCT t1.CustomerId
FROM tablename t1
WHERE NOT EXISTS (SELECT 1 FROM tablename t2 WHERE t2.CustomerId = t1.CustomerId AND t2.SectionId = 1)

Or, with conditional aggregation:

SELECT CustomerId
FROM tablename
GROUP BY CustomerId
HAVING COUNT(CASE WHEN SectionId = 1 THEN 1 END) = 0

Answer 2

Try this

select distinct id
from Test
where id not in (
    select distinct id
    from Test
    where section = 1
);

Answer 3

check 2 examples

Declare @t Table (CustomerId int,  SectionId int)

insert into @t Values
(1, 1),
(1, 2),
(1, 3),
(2, 2),
(2, 3),
(3, 1),
(3, 2),
(3, 3),
(4, 2),
(4, 3)

select DISTINCT CustomerId from @t 
where CustomerId not in (
    select CustomerId from @t
    where SectionId = 1
    group by CustomerId 
)


SELECT DISTINCT t1.CustomerId
FROM @t t1
WHERE NOT EXISTS (SELECT * FROM @t t2 
                  WHERE t2.CustomerId = t1.CustomerId AND t2.SectionId = 1)