Complex SQL syntax - django

Question

I have a game, and in the database I'm saving the user actions by date & time.
CREATE TABLE user_actions
(
aId BIGSERIAL PRIMARY KEY NOT NULL,
userId BIGINT NOT NULL REFERENCES users(uId) DEFERRABLE INITIALLY DEFERRED,
aDate TIMESTAMP without time zone DEFAULT now(),
aType INTEGER NOT NULL DEFAULT 0
);
My users are identified with email
CREATE TABLE users(
uId BIGSERIAL PRIMARY KEY NOT NULL,
uName VARCHAR (50) NOT NULL,
uEmail VARCHAR (75) UNIQUE NULL
);
and each day new prizes are added each day has a different number of prizes
CREATE TABLE prizes(
pId BIGSERIAL PRIMARY KEY NOT NULL,
pDate TIMESTAMP without time zone DEFAULT now(),
pType INTEGER NULL
pSize INTEGER NULL
);
This query list the userId and his last action date, per user
select distinct userId, max(aDate) from user_actions GROUP BY userId order by userId;
I want to create a query that will count the number of prizes added since each user last action.
I'm running:
OS: Debian
DB: Postgresql
code: Django

Answer 1

I think I will use CTE though It has not been tested
WITH last_actions AS (
SELECT DISTINCT userId, MAX(aDate) as last_logged
FROM user_actions
GROUP BY userId ORDER BY userId)
SELECT a.userId, COUNT(b.pDate)
FROM last_actions a, prizes b
WHERE b.pDate >= a.last_logged
GROUP BY a.userId;