One to Many MySQL [duplicate]

Answer 1

There is an example here that is almost exactly what you need foreign keys in innodb

CREATE TABLE parent (
  id INT NOT NULL,
  PRIMARY KEY (id)
) ENGINE=INNODB;

CREATE TABLE child (
  id INT,
  parent_id INT,
  INDEX par_ind (parent_id),
  FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE
) ENGINE=INNODB;

In your example user is the same as parent (a user has many locations, a parent has many childs) and location is the same as child (a location has one user, a child has one parent)