Please replace TAG ID 1 and TAG ID 2 by the tags you are looking for.
SELECT p.id
FROM wp_posts AS p
JOIN wp_term_relationships AS tr ON p.id = tr.object_id
JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
JOIN wp_terms AS t ON tt.term_id = t.term_id
WHERE t.term_id=_TAG ID 1_ OR t.term_id=_TAG ID 2_ AND p.post_type LIKE 'post'
GROUP BY p.id
HAVING COUNT( * ) >1