[LeetCode] 1581. Customer Who Visited but Did Not Make Any Transactions

문제 링크:
https://leetcode.com/problems/customer-who-visited-but-did-not-make-any-transactions/description/?envType=study-plan-v2&envId=top-sql-50

MySQL

SELECT A.customer_id
       , COUNT(A.visit_id) AS count_no_trans
FROM Visits A
LEFT JOIN Transactions B ON B.visit_id = A.visit_id
WHERE B.transaction_id IS NULL
GROUP BY A.customer_id