Getting a subquery to run N times - sql

Question

I'm trying to write a query that scans a table with multiple status entries for each date, for each test, for each area in a system. The goal being to get the newest status for each date for each test in ONE given area. This would allow me to get a broad overview of a system to determine where the majority of tests are failing
Below is the basic table structure, but I've created this SQLFiddle for ease of use.
CREATE TABLE area (
area_id integer NOT NULL,
area_name character varying(100)
);
CREATE TABLE test (
test_id integer NOT NULL,
test_name character varying(100) NOT NULL,
area_id integer NOT NULL,
test_isvisible boolean DEFAULT true
);
CREATE TABLE status (
status_date bigint NOT NULL,
test_id integer NOT NULL,
process_state_id integer NOT NULL,
process_step_id integer NOT NULL,
status_iteration integer DEFAULT 1 NOT NULL,
status_time bigint NOT NULL
);
CREATE TABLE process_state (
process_state_id integer NOT NULL,
process_state_name character varying(100)
);
CREATE TABLE process_step (
process_step_id integer NOT NULL,
process_step_name character varying(100)
);
The query I currently have gets the furthest point of test processing for one single test for every date that is available. I would like to figure out a way to get that same type of information but instead pass the id of a given area, so that I can get that same data for each test in that area.
I.E. in the SQLFiddle, where I have information from dates July 2 - 10 for test1, I would also like the query to return the same set of information for test2, thus returning 18 rows instead of 9.
The main problem I'm having is that when I try to just join the area table and get all of the tests that way, I end up getting only 9 days of data like I did with one test, but just a mix-and-match of data from different tests.
Let me know if you need any more information, and I will post back here if I manage to figure it out before someone here.
EDIT
As was pointed out in the comments, this trial data does not have keys (primary or foreign) simply because it saved time and wasn't necessary for the problem at hand. It is important to note though, that these keys are 100% necessary in real world application, as the larger the dataset becomes, the more unruly and time consuming it would be to run queries against your tables.
Lesson: Don't do drugs, do keys.

Answer 1

After a couple more hours, I found a different way to think about it, and finally got the data I was looking for.
I realized that my main problem with my previous attempts had been the use of GROUP BY, since I would have to group every selected column if I grouped any of them. So I first wrote a query that just got me the test_id/test_name along with each date that there was data for, since I knew I could group all of these no problem:
SELECT t.test_name AS test_name,
to_char( to_timestamp(s.status_date)::TIMESTAMP, 'MM/DD/YYYY' ) AS event_date,
s.status_date
FROM status s
INNER JOIN test t ON t.test_id = s.test_id
INNER JOIN area a ON a.area_id = t.area_id
INNER JOIN process_step step ON s.process_step_id = step.process_step_id
INNER JOIN process_state state ON s.process_state_id = state.process_state_id
WHERE a.area_id = 12
GROUP BY t.test_id, s.status_date, t.test_name;
This didn't give me any information about where that test made it through (completed, failed, running). So then I wrote a separate query that simply got the test status when it was given a test_id and a status_date:
SELECT
CASE WHEN state.process_state_name = 'FAILURE' OR state.process_state_name = 'WAITING' OR state.process_state_name = 'VOLUME' THEN state.process_state_name
WHEN step.process_step_name = 'COMPLETE' AND (state.process_state_name = 'SUCCESS' OR state.process_state_name = 'APPROVED') THEN 'Complete'
ELSE 'Running'
END AS process_state
FROM status s
INNER JOIN process_step step ON s.process_step_id = step.process_step_id
INNER JOIN process_state state ON s.process_state_id = state.process_state_id
WHERE s.test_id = 290
AND s.status_date = 1404273600
AND s.status_iteration = (SELECT MAX(s.status_iteration)
FROM status s
WHERE s.test_id = 290
AND s.status_date = 1404273600)
ORDER BY s.status_time DESC, s.process_step_id DESC, s.process_step_id DESC
LIMIT 1;
So this query worked for one single test and date, which I recognized would work perfectly for a subquery in my original query, since it would bypass the GROUP BY logic. So with that in mind, I proceeded to merge the two queries to get this one final query:
SELECT t.test_name AS test_name,
to_char( to_timestamp(status.status_date)::TIMESTAMP, 'MM/DD/YYYY' ) AS event_date,
(
SELECT
CASE WHEN state.process_state_name = 'FAILURE' OR state.process_state_name = 'WAITING' OR state.process_state_name = 'VOLUME' THEN state.process_state_name
WHEN step.process_step_name = 'COMPLETE' AND (state.process_state_name = 'SUCCESS' OR state.process_state_name = 'APPROVED') THEN 'Complete'
ELSE 'Running'
END AS process_state
FROM status s
INNER JOIN process_step step ON s.process_step_id = step.process_step_id
INNER JOIN process_state state ON s.process_state_id = state.process_state_id
WHERE s.test_id = t.test_id
AND s.status_date = status.status_date
AND s.status_iteration = (SELECT MAX(s.status_iteration)
FROM status s
WHERE s.test_id = t.test_id
AND s.status_date = status.status_date)
ORDER BY s.status_time DESC, s.process_step_id DESC, s.process_step_id DESC
LIMIT 1
) AS process_status
FROM status status
INNER JOIN test t ON t.test_id = status.test_id
INNER JOIN area a ON a.area_id = t.area_id
WHERE a.area_id = 12
GROUP BY t.test_id, status.status_date, t.test_name
ORDER BY 1, 2;
And all of this can be seen in action in my revised SQLFiddle.
Let me know if you have questions about what I did, hopefully this helps future developers.