SQL实现LeetCode(182.重复的邮箱)
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2022-06-24 19:56:23
[leetcode] 182.duplicate emails 重复的邮箱write a sql query to find all duplicate emails in a table named...
[leetcode] 182.duplicate emails 重复的邮箱
write a sql query to find all duplicate emails in a table named person.
+----+---------+
| id | email |
+----+---------+
| 1 | a@b.com |
| 2 | c@d.com |
| 3 | a@b.com |
+----+---------+
for example, your query should return the following for the above table:
+---------+
| email |
+---------+
| a@b.com |
+---------+
note: all emails are in lowercase.
这道题让我们求重复的邮箱,那么最直接的方法就是用group by...having count(*)...的固定搭配来做,代码如下:
解法一:
select email from person group by email having count(*) > 1;
我们还可以用内交来做,用email来内交两个表,然后返回id不同的行,则说明两个不同的人使用了相同的邮箱:
解法二:
select distinct p1.email from person p1 join person p2 on p1.email = p2.email where p1.id <> p2.id;
参考资料:
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