I have Problems with a select statement, as a little help here are the important columns:
Table1
ID NAME
TABLE 2
ID U_ID COUNTER
The ID of Table 1 Matches the U_ID of Table 2. Table 2 contains many entries for the same u_id.
What I want to do is to get the Name of the "user" (table 1) who has in sum the max. counter.
What I got since now is the join of the tables (Where clause depends on other rows which are not important for the problem).
Can anyone help me on this issue?
SELECT name,
SUM(counter) as counter
FROM table1
JOIN table2
ON table1.id = table2.u_id
GROUP BY u_id
ORDER BY counter DESC
LIMIT 1
You can try this:
SELECT name, SUM(counter) as total_counter
FROM table1
JOIN table2
ON table1.id = table2.u_id
GROUP BY u_id
ORDER BY total_counter DESC
LIMIT 1
Working Demo: http://sqlfiddle.com/#!2/45419/4
So what you need is an aggregate of an aggregate (max of sum of column). The easiest will be to create a view providing the sum and u_id end then select the max of it:
create view table2sums
as
select u_id, sum(counter) as total
from table2
group by u_id;
and then
select t1.name
from table1 t1, table2sums t2
where t1.id = t2.u_id
and t2.total >= all (
select total
from table2sums
)
In this special case you can also do it directly:
select t1.name
from table1 t1, table2 t2
where t1.id = t2.u_id
group by t1.name
having sum(t2.counter) >= all (
select sum(counter)
from table2
group by t2.u_id
)
NOTE: The other proposed solutions will show a better performance. My solution only selects the name (which is what you said you wanted) and works in any RDBMS. There exist RDBMS without the LIMIT possibility. In the end, I'd say: regard my solution as educational, the others as practical