Question

I have a table like this

Table A:

Id Count
1  4
1  16
1  8
2  10
2  15
3  18
etc

Table B:
1 sample1.file
2 sample2.file
3 sample3.file

TABLE C:
Count fileNumber
16 1234
4 2345
15 3456
18 4567

and so on…

What I want is this

1 sample1.file 1234
2 sample2.file 3456
3 sample3.file 4567

To get the max value from table A I used

  Select MAX (Count) from A where Id='1'

This works well but my problem is when combining data with another table.

When I join Table B and Table A, I need to get the MAX for all Ids and in my query I dont know what Id is.

This is my query

SELECT B.*,C.*
JOIN A on A.Id = B.ID
JOIN C on A.id = B.ID
WHERE (SELECT MAX(COUNT) 
         FROM A 
        WHERE Id = <what goes here????>)

To summarise, what I want is Values from Table B, FileNumber from Table c (where the count is Max for ID from table A).

UPDATE: COrrecting table C above. Looks like I need Table A.

Answer 1

I think this is the query you’re looking for:

select b.*, c.filenumber from b
join (
  select id, max(count) as count from a
  group by id
) as NewA on b.id = NewA.id
join c on NewA.count = c.count

However, you should take into account that I don’t get why for id=1 in tableA you choose the 16 to match against table C (which is the max) and for id=2 in tableA you choose the 10 to match against table C (which is the min). I assumed you meant the max in both cases.

Edit:

I see you’ve updated tableA data. The query results in this, given the previous data:

+----+---------------+------------+
| ID |   FILENAME    | FILENUMBER |
+----+---------------+------------+
|  1 | sample1.file  |       1234 |
|  2 | sample2.file  |       3456 |
|  3 | sample3.file  |       4567 |
+----+---------------+------------+

Here is a working example