Given m2m relation: items-categories I have three tables:
I want to find an item belonging to all given category sets:
Find Item
belonging to a category in [1,3,6]
and belonging to a category in [7,8,4]
and belonging to a category in [12,66,42]
and ...
There are two ways I can think of to accomplish this in mySQL.
OPTION A: INNER JOIN:
SELECT id from items
INNER JOIN category c1 ON (item.id = c1.item_id)
INNER JOIN category c2 ON (item.id = c2.item_id)
INNER JOIN category c3 ON (item.id = c3.item_id)
...
WHERE
c1.category_id IN [1,3,6] AND
c2.category_id IN [7,8,4] AND
c3.category_id IN [12,66,42] AND
...;
OPTION B: EXISTS:
SELECT id from items
WHERE
EXISTS(SELECT category_id FROM category WHERE category.item_id = id AND category_id in [1,3,6] AND
EXISTS(SELECT category_id FROM category WHERE category.item_id = id AND category_id in [7,8,4] AND
EXISTS(SELECT category_id FROM category WHERE category.item_id = id AND category_id in [12,66,42] AND
...;
Both options work. The question is: Which is the fastest / most optimal for large item table? Or is there an OPTION C I am missing?
OPTION A
JOIN
has an advantage over EXIST
, because it will more efficiently use the indices, especially in case of large tables