SQL function-like WHERE statement - sql

Question

I've researched for a pretty long time and extensively already on this problem; so far nothing similar has come up. tl;dr below
Here's my problem below.
I'm trying to create a SELECT statement in SQLite with conditional filtering that works somewhat like a function. Sample pseudo-code below:
SELECT col_date, col_hour FROM table1 JOIN table2
ON table1.col_date = table2_col_date AND table1.col_hour = table2.col_hour AND table1.col_name = table2.col_name
WHERE
IF table2.col_name = "a" THEN {filter these records further such that its table2.col_volume >= 600} AND
IF table2.col_name = "b" THEN {filter these records further such that its table2.col_volume >= 550}
BUT {if any of these two statements are not met completely, do not get any of the col_date, col_hour}
*I know SQLite does not support the IF statement but this is just to demonstrate my intention.
Here's what I've been doing so far. According to this article, it is possible to transform CASE clauses into boolean logic, such that you will see here:
SELECT table1.col_date, table1.col_hour FROM table1 INNER JOIN table2
ON table1.col_date = table2.col_date AND table1.col_hour = table2.col_hour AND table1.col_name = table2.col_name
WHERE
((NOT table2.col_name = "a") OR table2.col_volume >= 600) AND
((NOT table2.col_name = "b") OR table2.col_volume >= 550)
In this syntax, the problem is that I still get col_dates and col_hours where at least one col_name's col_volume for that specific col_date and col_hour did not meet its requirement. (e.g. I still get a record entry with col_date = 2010-12-31 and col_hour = 5, but col_name = "a"'s col_volume = 200 while col_name = "b"'s col_volume = 900. This said date and hour should not appear in the query because "a" has a volume which is not >= 600, even if "b" met its volume requirement which is >= 550.)
For tl;dr
If all these are getting confusing, here are sample tables with the sample correct query results so you can just forget everything above and go right on ahead:
table1
col_date,col_hour,col_name,extra1,extra2
2010-12-31,4,"a","hi",1
2010-12-31,4,"a","he",1
2010-12-31,4,"a","ho",1
2010-12-31,5,"a","hi",1
2010-12-31,5,"a","he",1
2010-12-31,5,"a","ho",1
2010-12-31,6,"a","hi",1
2010-12-31,6,"a","he",1
2010-12-31,6,"a","ho",1
2010-12-31,4,"b","hi",1
2010-12-31,4,"b","he",1
2010-12-31,4,"b","ho",1
2010-12-31,5,"b","hi",1
2010-12-31,5,"b","he",1
2010-12-31,5,"b","ho",1
2010-12-31,6,"b","hi",1
2010-12-31,6,"b","he",1
2010-12-31,6,"b","ho",1
table2
col_date,col_hour,col_name,col_volume
2010-12-31,4,"a",750
2010-12-31,4,"b",750
2010-12-31,5,"a",200
2010-12-31,5,"b",900
2010-12-31,6,"a",700
2010-12-31,6,"b",800
The correct query results (with col_volume filters: 600 for 'a' and 550 for 'b') should be:
2010-12-31,4
2010-12-31,6

Answer 1

try this:
SELECT table1.col_date,
table1.col_hour
FROM table1
INNER JOIN table2
ON table1.col_date = table2.col_date
AND table1.col_hour = table2.col_hour
AND table1.col_name = table2.col_name
WHERE EXISTS ( -- here I'm appling the filter logic
select col_date,
col_hour
from table2 sub
where (col_name = 'a' and col_volume >= 600)
or (col_name = 'b' and col_volume >= 550)
and sub.col_date = table2.col_date
and sub.col_hour = table2.col_hour
and sub.col_name = table2.col_name
group by col_date,
col_hour
having count(1) = 2 -- I assume there could be only two rows:
-- one for 'a' and one for 'b'
)
You can check this demo in SQLfiddle
Last thing, you show the same columns from Table1 that you use for the join, but I imagine this is just for the sake of this example

Answer 2

You can try with exists and correlated subquery with case for different conditions in the where clause:
select t1.col_date
, t1.col_hour
from table1 t1
where exists ( select t2.col_volume
from table2 t2
where t2.col_date = t1.col_date
and t2.col_hour = t1.col_hour
and t2.col_name in ('a', 'b')
group by t2.col_volume
having count(t2.col_name >= case when t2.col_name = 'a' then 600 else 550 end) = (select count(*) from table2 where col_name = t2.col_name))

Answer 3

Your boolean transformation is wrong.
Your IFs infer that you are looking for rows that:
table2.col_name = "a" and col_volume >= 600
table2.col_name = "b" and col_volume >= 550
(implicitly) other values for col_name
So, to translate this to SQL:
SELECT table1.col_date, table1.col_hour
FROM table1
INNER JOIN table2 ON table1.col_date = table2.col_date AND
table1.col_hour = table2.col_hour
WHERE (table2.col_name = 'a' AND table2.col_volume >= 600) OR
(table2.col_name = 'b' AND table2.col_volume >= 550) OR
(table2.col_name NOT IN ('a', 'b'))

Answer 4

I think I have an answer (BIG HELP to #mucio's "HAVING" clause; looks like I have to brush up on that).
Apparently the approach was a simple sub-query in which the outer query will do a join on. It's a work-around (not really a direct answer to the problem I posted, I had to reorganize my program flow with this approach), but it got the job done.
Here's the sample code:
SELECT table1.col_date, table1.col_hour
FROM table1
INNER JOIN
(
SELECT col_date, col_hour
FROM table2
WHERE
(col_name = 'a' AND col_volume >= 600) OR
(col_name = 'b' AND col_volume >= 550)
GROUP BY col_date, col_hour
HAVING COUNT(1) = 2
) tb2
ON
table1.col_date = tb2.col_date AND
table1.col_hour = tb2.col_hour
GROUP BY table1.col_date, table1.col_hour