таблица user
+------+---------------+---------+
| id   |   users   |  gender   |
+----+---------------+-----------+
|  1   | Lesha       |     1     |
|  2   | Pavel       |     1     |
|  3   | Masha       |     2     |
|  4   | Kolya       |     1     |
+------+-------------+-----------+

таблица gender
+----+--------------+
| id | user_gend    |
+----+--------------+
|  1 | мужик        | 
|  2 | девка        |
+----+--------------+

1)SELECT gender From user WHERE users = "Марина" 

2)SELECT users , user_gend FROM user LEFT JOIN gender ON
user.gender = gender.id

Ответ SELECT users , user_gend FROM user LEFT JOIN gender ON
user.gender = gender.id WHERE user.users = "Марина"