From: | Lee Hachadoorian <lee(dot)hachadoorian(at)gmail(dot)com> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Aggregating by unique values |
Date: | 2010-12-14 05:11:17 |
Message-ID: | 4D06FC75.1050209@gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-sql |
Hello,
I'm trying to count customers who have received services by ZIP code,
but I want to count each customer only once even though customers may
have received services on multiple dates, and therefore appear in the
table multiple times. There *is* a separate customers table, but because
of dirty data, I cannot rely on it.
The best I can come up with is:
SELECT
zip, count(*) AS count_serviced
FROM
(SELECT DISTINCT zip, id FROM customer_service_date) a
GROUP BY
zip
;
The table (with some irrelevant fields dropped) is:
CREATE TABLE customer_service_date
(
id integer,
address character varying,
city character varying,
state character varying,
zip character varying,
service_date date
)
;
The table is missing a primary key field, but it would be (id,
service_date) if it had one.
Any suggestions to improve this?
Thanks,
--Lee
--
Lee Hachadoorian
PhD Student, Geography
Program in Earth & Environmental Sciences
CUNY Graduate Center
From | Date | Subject | |
---|---|---|---|
Next Message | Jasen Betts | 2010-12-14 07:12:31 | Re: constraint with check |
Previous Message | Viktor Bojović | 2010-12-13 23:36:57 | constraint with check |