MySQL - OR

"users" table:

user_id	name	city	age
1	John Doe	New York	15
2	Jimmy McNulty	Los Angeles	44
2	Andrew Wilkins	Chicago	15
2	Bob Seizmore	New York	16

SELECT * FROM users
WHERE age<18
AND city='New York'
OR city='Chicago';

Result:

user_id	name	city	age
1	John Doe	New York	15
2	Bob Seizmore	New York	16
2	Andrew Wilkins	Chicago	15