Getting A Count In One SQL Statement

Question

Since I don't know how to do what I'm about to ask, I would normally create a table (tbl1) with the main dataset I want and then create a second table (tbl2) with additional data I want, join the two and update tbl1 data with tbl2 data.
However, I would like to know how to do this in one SQL statement. I somehow need to link the count sql with the main body..?
So..I have to pull data by group id. Each group id can have a certain number of active members in it. I would like to use one SQL statement to pull the group id's and also, at the same time, give me a count of each group's active membership. Both the main and count statments in the below SQL include the emp_grps table which can obviously be linked so the right groups are updated..
Not sure how to begin to reflect this in an SQL statement, so I'll just give you the wrong version to show what data elements I have. The following gives the total count by all group's in each groups individual record. Of course, as mentioned, all I want is that group's share of the membership in their individual record:
select group_id,
(select count(*)
from elig elg
join emp_grps eg
on elg.group_id = eg.group_id
where eg.rmc_code in ('CR')
and elg.elig_start_date < sysdate
and elg.elig_end_date > sysdate) mbr_count
from odw.emp_grps eg
where eg.rmc_code in ('1M')
Output from this query:
GROUP_ID MBR_COUNT
A 10,000
B 10,000
C 10,000
D 10,000
What I want to see:
GROUP_ID MBR_COUNT
A 7,000
B 1,000
C 1,500
D 500
Thanks for any assistance..

Answer 1

Hi,
So you want one row for every distinct value of group_id, with a count that reflects just that group_id.
That sound like a job for GROUP BY group_id and the aggregate COUNT function, like this:
SELECT    eg.group_id
,       COUNT ( CASE
                  WHEN  eg.rmc_code  IN ('CR')
                THEN  1
              END
            )     AS mbr_count
FROM        elig           elg
JOIN       emp_grps      eg    ON   elg.group_id  = eg.group_id
WHERE       eg.rmc_code             IN ('CR', '1M')
AND       elg.elig_start_date < SYSDATE
AND       elg.elig_end_date   > SYSDATE
GROUP BY  eg.group_id
HAVING       COUNT ( CASE
                  WHEN  eg.rmc_code  IN ('1M')
                THEN  1
              END
            ) > 1
ORDER BY  eg.group_id
;It's unclear what you're trying to do with eg.rmc_code. I'm guessing you want to count the rows where it's one value ('CR'), but only display groups that also have another value ('1M').
Of course, I can't say for sure without seeing your actual tables, or at least small test versions of them.
Post CREATE TABLE and INSERT statements (relevant columns only) for all tables involved, and the resutls you want from that sample data (if it's not the results you already posted).
Always say which version of Oracle you're using.