Question

I have a sql server query question. I have a table like below. Giving a parameter to stored procedure, I need to query mutual CustomFields in lists that I want. For example, if ListID is given 1 and 2 and 3, result table will have columns that gives me ‘FullName’ in that case, because only ‘FullName’ is in all three ID’s. I did that which solved the issue somehow, but looking for a better and precise practice. Thanks

SELECT DISTINCT(CustomField) 
FROM CustomFields a
WHERE EXISTS (
      SELECT count(*) 
      FROM CustomFields b 
      WHERE a.CustomField = b.CustomField 
      HAVING count(*)>2
)
ORDER BY a.CustomField


CustomField   ListID
PhoneNumber   1
Unvan         1
FullName      2
Surname       2
Regiob        2
FullName      3
BirthPlace    3
FullName      1

Answer 1

Here’s a more common approach to find CustomFields that are in groups 1, 2 and 3:

SELECT  CustomField
FROM    CustomFields
WHERE   ListID in (1,2,3)
GROUP BY
        CustomField
HAVING  COUNT(DISTINCT ListId) = 3

No subquery required, and the where clause filters out uninteresting groups before the group by.