Hello, > I have a complex query question whose answer I think would help me to > understand subselects and aggregates better. I have a table with four > columns of interest: > > id (int primary key), loc_title (varchar null), loc_value (float > null), loc_unit (varchar null) > > I want the output columns to be: > (1) each distinct value of loc_title, sorted > (2) an id of a record containing that loc_title > (3) the loc_value for the record in column 2 > (4) the loc_unit for the record in column 2 > > I don't care as much how the records for columns 2-4 are chosen. It > could be max(loc_value), min(id), or something else. I just need some > sample records to test my program against. > > Is this something I should be able to do with a single query with a > subselect, or is it too much for one query? I tried a few ways and > none of them were syntactically valid. Will this do? test=# select * from myt; id | loc_title | loc_value | loc_unit ----+-----------+-----------+---------- 1 | AA | 80 | 10 2 | AA | 80 | 10 3 | BB | 80 | 10 4 | AA | 80 | 10 5 | BB | 80 | 10 (5 rows)
test=# select a.* from myt a where id in (select min(id) from myt group by loc_title) order by loc_title; id | loc_title | loc_value | loc_unit ----+-----------+-----------+---------- 1 | AA | 80 | 10 3 | BB | 80 | 10 (2 rows)
Regards, Jayadevan
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