Re: Tricky SQL problem - retrieve information_schema info and make use of it.
От | Paul Linehan |
---|---|
Тема | Re: Tricky SQL problem - retrieve information_schema info and make use of it. |
Дата | |
Msg-id | CAF4RT5Qod85UkNbo7BAPfVk_pfdX1TZN2iqu2vcqabeM0g4efQ@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: Tricky SQL problem - retrieve information_schema info and make use of it. (Paul Linehan <linehanp@tcd.ie>) |
Ответы |
Re: Tricky SQL problem - retrieve information_schema info
and make use of it.
|
Список | pgsql-novice |
Hi all, I have an easy problem - just can't get my head around it. I have a domain id and a date - what I want is the 3 highest dates by domain id. I prepared a complete schema (see below). The result I want is 1, 2016-02-24 1, 2016-02-25 1, 2016-02-26 2, 2016-02-25 2, 2016-02-26 2, 2016-02-27 3, 2016-03-27 3, 2016-03-28 3, 2016-03-29 I've tried a couple of things, but my brain isn't working tonight :-) select max(distinct(domain_id)), max(d_date) from dom_test group by domain_id, d_date limit 3; select domain_id, max(d_date) from ( select distinct(domain_id), d_date from dom_test group by domain_id ) tab; My schema. create table dom_test(domain_id int, d_date date); insert into dom_test values(1, '2016-02-23'); insert into dom_test values(1, '2016-02-24'); insert into dom_test values(1, '2016-02-25'); insert into dom_test values(1, '2016-02-26'); insert into dom_test values(2, '2016-02-23'); insert into dom_test values(2, '2016-02-24'); insert into dom_test values(2, '2016-02-25'); insert into dom_test values(2, '2016-02-26'); insert into dom_test values(2, '2016-02-27'); insert into dom_test values(3, '2016-02-23'); insert into dom_test values(3, '2016-02-24'); insert into dom_test values(3, '2016-02-25'); insert into dom_test values(3, '2016-02-26'); insert into dom_test values(3, '2016-03-27'); insert into dom_test values(3, '2016-03-28'); insert into dom_test values(3, '2016-03-29');
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