9/3 每日一題(MYSQL 正則表達式 檢查信箱格式)

#必須以字母開頭,可能包含'_', '.',  '-' 三種符號, 必須以@leetcode.com 結尾

Table: Users

+---------------+---------+
| Column Name   | Type    |
+---------------+---------+
| user_id       | int     |
| name          | varchar |
| mail          | varchar |
+---------------+---------+
user_id is the primary key (column with unique values) for this table.
This table contains information of the users signed up in a website. Some e-mails are invalid.

 

Write a solution 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 result format is in the following example.

 

Example 1:

Input: 
Users table:
+---------+-----------+-------------------------+
| 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     |
+---------+-----------+-------------------------+
Output: 
+---------+-----------+-------------------------+
| user_id | name      | mail                    |
+---------+-----------+-------------------------+
| 1       | Winston   | winston@leetcode.com    |
| 3       | Annabelle | bella-@leetcode.com     |
| 4       | Sally     | sally.come@leetcode.com |
+---------+-----------+-------------------------+
Explanation: 
The mail of user 2 does not have a domain.
The mail of user 5 has the # sign which is not allowed.
The mail of user 6 does not have the leetcode domain.
The mail of user 7 starts with a period.

 

# Write your MySQL query statement below

SELECT user_id , name, mail

FROM Users

WHERE mail REGEXP '^[A-Za-z][A-Za-z0-9_.-]*@leetcode\\.com$'

-------------------------

SELECT * FROM users WHERE mail REGEXP '^[a-zA-Z][a-zA-Z-._0-9]*@leetcode[.]{1}com$'