LeetCode（数据库）- 进店却未进行过交易的顾客

题目链接：​​点击打开链接​​

题目大意：略。

解题思路：略。

AC 代码

SELECT customer_id, COUNT(*) count_no_trans
FROM Visits
WHERE visit_id NOT IN (SELECT DISTINCT visit_id FROM Transactions)
GROUP BY customer_id