LeetCode-查詢重複的電子郵箱(duplicate-emails)
阿新 • • 發佈：2018-12-18
題目難度： 簡單
編寫一個 SQL 查詢，查詢 Person 表中所有重複的電子郵箱。
示例：
+----+---------+
| Id | Email |
+----+---------+
| 1 | [email protected] |
| 2 | [email protected] |
| 3 | [email protected] |
+----+---------+
根據以上輸入，你的查詢應返回以下結果：
+---------+ | Email | +---------+ | [email protected] | +---------+
**說明：**所有電子郵箱都是小寫字母。
Solution
Language: MySQL
# 1st
SELECT Email FROM Person GROUP BY Email
HAVING COUNT(*) > 1;
# 2nd
SELECT DISTINCT p1.Email FROM Person p1
JOIN Person p2 ON p1.Email = p2.Email
WHERE p1.Id <> p2.Id;