Re: Doing a conditional aggregate (e.g. count(*) if x=y) in postgres?

Bryce Nesbitt wrote:
> All;
> Is there a way to get a conditional aggregate? I have this two column view:
>
> SELECT count(*) AS count, xx_plan.plan_name
> FROM xx_membership
> JOIN xx_account USING (account_id)
> JOIN xx_plan USING (plan_id)
> WHERE xx_membership.status = 10
> GROUP BY xx_plan.plan_name;
>
> And would like to add additional columns (not rows) breaking out
> "status=20" and "status=30" totals.
> Is this possible without a stored procedure?

SELECT sum(CASE WHEN xx_membership.status = 10 THEN 1 ELSE 0 END) AS sum10,
sum(CASE WHEN xx_membership.status = 20 THEN 1 ELSE 0 END) AS sum20,
sum(CASE WHEN xx_membership.status = 30 THEN 1 ELSE 0 END) AS sum30,
xx_plan.plan_name
FROM xx_membership
JOIN xx_account USING (account_id)
JOIN xx_plan USING (plan_id)
WHERE xx_membership.status IN (10,20,30)
GROUP BY xx_plan.plan_name;

You may or may not care about including the WHERE clause there depending
upon its selectivity and whether there's an index for the planner to use.

HTH,
Geoff