Sql-server – Running a query on the results of another query

querysql serversubquerysyntax

I have 2 queries, they both run fine and pull the results I'm looking for. However, I need to be able to run one query from the results of another. This is t-sql/mssql/sybase

For example, the following query works to count the number of times/rows a each value shows up in the 'referred_link' column of the cases table, and show me only those that appear 3 or more times:

SELECT cases.referred_link, count(*)
FROM CASES
GROUP BY referred_link
HAVING COUNT(*) >= 3

The next query pulls a bunch of data from various tables and filters down on the required criteria. The catch is, I only want this 2nd query to run on the results from the first query… items which show up 3+ times on the referred_link table. 

select * from cases inner join names on cases.referred_link=names.names_id
left join (select * from mailing_list_defined where mailing_list='home_addr') a
on names.names_id=a.names_id
left join party on cases.casenum=party.case_id
where names.person='Y' and date_opened>=today()-6 and party.our_client='Y' and party.role='Plaintiff'

I tried something like this (doesn't work, of course):

select * from cases inner join names on cases.referred_link=names.names_id
left join (select * from mailing_list_defined where mailing_list='Mattar Stars') a
on names.names_id=a.names_id
left join party on cases.casenum=party.case_id
where names.person='Y' and date_opened>=today()-6 and party.our_client='Y' and party.role='Plaintiff'
and names_id IN (SELECT cases.referred_link, count(*)
                FROM CASES
                GROUP BY referred_link
                HAVING COUNT(*) >= 3)

Can anybody point me in the correct direction for how this could be accomplished?

Best Answer

When you put a subquery between IN(…), you have to ensure it returns exactly one column. Going by your other query, it seems cases.referred_link is actually already a names_id, so you are already pretty much there. All you need to do is remove that extra count(*) from the list of selected columns.

… and names.names_id IN (SELECT cases.referred_link
                FROM CASES
                GROUP BY referred_link
                HAVING COUNT(*) >= 3)
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