MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    buyer_name VARCHAR(255) NOT NULL,
    phone_number VARCHAR(20) NOT NULL
);
INSERT INTO users (buyer_name, phone_number) VALUES 
('Doni', '6281234567'),
('sofia', '6281234568'),
('Sofia', '6281234568'),
('Sophia', '6281234568');

Records: 4  Duplicates: 0  Warnings: 0


SELECT * FROM users;


id
buyer_name
phone_number


1
Doni
6281234567

2
sofia
6281234568

3
Sofia
6281234568

4
Sophia
6281234568


SELECT
    MIN(buyer_name) AS buyer_name,
    phone_number
FROM
    users
GROUP BY
    phone_number;


buyer_name
phone_number


Doni
6281234567

sofia
6281234568

id	buyer_name	phone_number
1	Doni	6281234567
2	sofia	6281234568
3	Sofia	6281234568
4	Sophia	6281234568