Is there a Union that calculates convergence of samples?

Question

MySQL

There are 2+ samples

SELECT productId FROM product WHERE (condition #1)
SELECT productId FROM product WHERE (condition #2)
...

UNION gets all values ​​from two samples. And I need to get convergence from the selections, in simple words, something like array_intersect in php for arrays, but only for queries.

Answer 1

How to emulate the MySQL INTERSECT operator