Find records with exact matches on a many to many relationship - sql

Question

I have three tables that look like these:
PROD
Prod_ID|Desc
------------
P1|Foo1
P2|Foo2
P3|Foo3
P4|Foo4
...
RAM
Ram_ID|Desc
------------
R1|Bar1
R2|Bar2
R3|Bar3
R4|Bar4
...
PROD_RAM
Prod_ID|Ram_ID
------------
P1|R1
P2|R2
P3|R1
P3|R2
P3|R3
P4|R3
P5|R1
P5|R2
...
Between PROD and RAM there's a Many-To-Many relationship described by the PROD_RAM table.
Given a Ram_ID set like (R1,R3) I would like to find all the PROD that has exactly ONE or ALL of the RAM of the given set.
Given (R1,R3) should return for example P1,P4 and P5; P3 should not be returned because has R1 and R3 but also R2.
What's the fastest query to get all the PROD that has exactly ONE or ALL of the Ram_ID of a given RAM set?
EDIT:
The PROD_RAM table could contain relationship bigger than 1->3 so, "hardcoded" checks for count = 1 OR = 2 are not a viable solution.

Answer 1

Another solution you could try for speed would be like this
;WITH CANDIDATES AS (
SELECT pr1.Prod_ID
, pr2.Ram_ID
FROM PROD_RAM pr1
INNER JOIN PROD_RAM pr2 ON pr2.Prod_ID = pr1.Prod_ID
WHERE pr1.Ram_ID IN ('R1', 'R3')
)
SELECT *
FROM CANDIDATES
WHERE CANDIDATES.Prod_ID NOT IN (
SELECT Prod_ID
FROM CANDIDATES
WHERE Ram_ID NOT IN ('R1', 'R3')
)
or if you don't like repeating the set conditions
;WITH SUBSET (Ram_ID) AS (
SELECT 'R1'
UNION ALL SELECT 'R3'
)
, CANDIDATES AS (
SELECT pr1.Prod_ID
, pr2.Ram_ID
FROM PROD_RAM pr1
INNER JOIN PROD_RAM pr2 ON pr2.Prod_ID = pr1.Prod_ID
INNER JOIN SUBSET s ON s.Ram_ID = pr1.Ram_ID
)
, EXCLUDES AS (
SELECT Prod_ID
FROM CANDIDATES
LEFT OUTER JOIN SUBSET s ON s.Ram_ID = CANDIDATES.Ram_ID
WHERE s.Ram_ID IS NULL
)
SELECT *
FROM CANDIDATES
LEFT OUTER JOIN EXCLUDES ON EXCLUDES.Prod_ID = CANDIDATES.Prod_ID
WHERE EXCLUDES.Prod_ID IS NULL

Answer 2

One way to do this would be something like the following:
SELECT PROD.Prod_ID FROM PROD WHERE
(SELECT COUNT(*) FROM PROD_RAM WHERE PROD_RAM.Prod_ID = PROD.Prod_ID) > 0 AND
(SELECT COUNT(*) FROM PROD_RAM WHERE PROD_RAM.Prod_ID = PROD.Prod_ID AND PROD.Ram_ID <>
IFNULL((SELECT TOP 1 Ram_ID FROM PROD_RAM WHERE PROD_RAM.Prod_ID = PROD.Prod_ID),0)) = 0

Answer 3

SELECT Prod_ID
FROM
( SELECT Prod_ID
, COUNT(*) AS cntAll
, COUNT( CASE WHEN Ram_ID IN (1,3)
THEN 1
ELSE NULL
END
) AS cntGood
FROM PROD_RAM
GROUP BY Prod_ID
) AS grp
WHERE cntAll = cntGood
AND ( cntGood = 1
OR cntGood = 2 --- number of items in list (1,3)
)
Not at all sure if it's the fastest way. You'll have to try different ways to write this query (using JOINs and NOT EXISTS ) and test for speed.