On Wed, Oct 26, 2016 at 9:22 AM, Tim Smith <randomdev4+postg...@gmail.com> wrote:
> Hi, > > I've been trying various GROUP BY but these all end up erroring out, > so maybe I'm using the wrong tool for the job (or, more likely, the > required query is beyond my level of SQL-fu !). > > CREATE TABLE IF NOT EXISTS names ( > main_id bigint, > sub_id bigint, > name text > ); > > create unique index IF NOT EXISTS name_idx on names(main_id,sub_id); > insert into names(main_id,sub_id,name) values(1,2,'Bob'); > insert into names(main_id,sub_id,name) values(1,1,'Baby Bob'); > insert into names(main_id,sub_id,name) values(100,200,'Tom'); > insert into names(main_id,sub_id,name) values(100,100,'Jerry'); > > > The desired output is one row per main_id, with the desired row being > the one with the lowest sub_id, i.e. > > select....... > > main_id | sub_id | name > ---------+------------+------------------- > 1 | 1 | Baby Bob > 100 | 100 | Jerry > > Try (not tested): SELECT DISTINCT ON (main_id) main_id, sub_id, name FROM names ORDER BY main_id, sub_id ASC; David J.
