中間テーブルには複合インデックスと単一インデックスどちらを作成すれば良いのかで使用するsql

verification_sqls.md

JOINのみ

EXPLAIN ANALYZE SELECT
  *
FROM
  user_products AS up
JOIN
  users AS u
ON
  up.user_id = u.user_id
JOIN
  products AS p
ON
  up.product_id = p.product_id
;

JOINしてWHERE

EXPLAIN ANALYZE SELECT
  *
FROM
  user_products AS up
JOIN
  users AS u
ON
  up.user_id = u.user_id
JOIN
  products AS p
ON
  up.product_id = p.product_id
WHERE
  u.user_name = 'ユーザーNo.5000' AND
  p.product_name = 'プロダクトNo.5000'
;

WHEREのみ

EXPLAIN ANALYZE SELECT * FROM user_products WHERE user_id = 5000 AND product_id = 5000;