1517. Find Users With Valid E-Mails

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LeetCode

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Problem

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.

Example 1:

Input: 
Users table:
+---------+-----------+-------------------------+
| user_id | name      | mail                    |
+---------+-----------+-------------------------+
| 1       | Winston   | [email protected]    |
| 2       | Jonathan  | jonathanisgreat         |
| 3       | Annabelle | [email protected]     |
| 4       | Sally     | [email protected] |
| 5       | Marwan    | quarz#[email protected] |
| 6       | David     | [email protected]       |
| 7       | Shapiro   | [email protected]     |
+---------+-----------+-------------------------+
Output: 
+---------+-----------+-------------------------+
| user_id | name      | mail                    |
+---------+-----------+-------------------------+
| 1       | Winston   | [email protected]    |
| 3       | Annabelle | [email protected]     |
| 4       | Sally     | [email protected] |
+---------+-----------+-------------------------+
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.

Code

select user_id,name,mail
from users
where mail regexp("^[A-Z|a-z][ 0-9A-Za-z\\-\\.\\_]*@leetcode\\.com$")