文章目錄

• • 1. 題目
  • 2. 解題

1. 題目

Table: Users

+---------------+---------+ | Column Name | Type | +---------------+---------+ | user_id | int | | name | varchar | | mail | varchar | +---------------+---------+

user_id is the primary key for this table.
This table contains information of the users signed up in a website. Some e-mails are invalid.

Write an SQL query to find the users who have valid emails.

A valid e-mail has a prefix name and a domain where:

• The prefix name is a string that may contain letters (upper or lower case), digits, underscore '_', period '.' and/or dash '-'.
• The prefix name must start with a letter.
• The domain is '@leetcode.com'.

Return the result table in any order.

The query result format is in the following example.

Users +---------+-----------+-------------------------+ | user_id | name | mail | +---------+-----------+-------------------------+ | 1 | Winston | winston@leetcode.com | | 2 | Jonathan | jonathanisgreat | | 3 | Annabelle | bella-@leetcode.com | | 4 | Sally | sally.come@leetcode.com | | 5 | Marwan | quarz#2020@leetcode.com | | 6 | David | david69@gmail.com | | 7 | Shapiro | .shapo@leetcode.com | +---------+-----------+-------------------------+Result table: +---------+-----------+-------------------------+ | user_id | name | mail | +---------+-----------+-------------------------+ | 1 | Winston | winston@leetcode.com | | 3 | Annabelle | bella-@leetcode.com | | 4 | Sally | sally.come@leetcode.com | +---------+-----------+-------------------------+ The mail of user 2 doesn't have a domain. The mail of user 5 has # sign which is not allowed. The mail of user 6 doesn't have leetcode domain. The mail of user 7 starts with a period.

來源：力扣（LeetCode）
鏈接：https://leetcode-cn.com/problems/find-users-with-valid-e-mails
著作權歸領扣網絡所有。商業轉載請聯系官方授權，非商業轉載請注明出處。

2. 解題

語法規則：
https://www.runoob.com/mysql/mysql-regexp.html
https://www.cnblogs.com/zhaopanpan/p/10133224.html

^ 表示開頭 + 匹配一個或多個,不包括空 [] 表示集合里的任意一個 \\ 用于轉義特殊字符 a{m,n} 匹配m到n個a，左側不寫為0，右側不寫為任意 $ 表示以什么為結尾 # Write your MySQL query statement below select * from Users where mail regexp '^[a-zA-Z]+[a-zA-Z0-9_\\./\\-]{0,}@leetcode\\.com$' order by user_id

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