create table users_1 (
id_1 int (10)
); 

create table users_2 (
id_2 int (10),
number int(30),
name varchar(10)
); 

insert into users_1 values (1);
insert into users_1 values (2);
insert into users_1 values (3);
insert into users_2 values(1, 1111111111, 'Vasya');
insert into users_2 values(2, 1111111111, 'Vasya');
insert into users_2 values(3, 1111111111, 'Vasya');
---------------------------------------------------
SELECT *
FROM users_1 AS u1
    INNER JOIN users_2 AS u2 ON u2.id_2 = u1.id_1
WHERE u1.id_1 IN (SELECT MIN(id_2) FROM users_2 GROUP BY number);

SELECT *
FROM users_1 AS u1
    INNER JOIN users_2 AS u2 ON u2.id_2 = u1.id_1
WHERE u1.id_1 IN (SELECT MIN(id_2) FROM users_2 GROUP BY number);

SELECT *
FROM users_1 AS u1
  JOIN users_2 AS u2 ON u2.id_2 = u1.id_1
  JOIN (SELECT MIN(id_2) AS id_2 FROM users_2 GROUP BY number) t ON t.id_2=u1.id_1