CREATE TABLE interests (
	id INT UNSIGNED NOT NULL auto_increment,
	name VARCHAR( 50 ) NOT NULL,
	PRIMARY KEY (id),
	UNIQUE KEY (name)
) ENGINE=InnoDB;
CREATE TABLE users (
	id INT UNSIGNED NOT NULL auto_increment,
	name VARCHAR( 50 ) NOT NULL,
	-- password, etc.
	PRIMARY KEY (id),
	UNIQUE KEY (name)
) ENGINE=InnoDB;
CREATE TABLE users_interests (
	user_id INT UNSIGNED NOT NULL,
	interest_id INT UNSIGNED NOT NULL,
	PRIMARY KEY (user_id, interest_id),
	CONSTRAINT FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE,
	CONSTRAINT FOREIGN KEY (interest_id) REFERENCES interests (id) ON DELETE CASCADE
) ENGINE=InnoDB;

CREATE TEMPORARY TABLE tui (
	interest_name VARCHAR( 50 ) NOT NULL,
	UNIQUE KEY(interest_name)
);

START TRANSACTION

INSERT INTO users (name, ...) VALUES ('Vasja', ...)

INSERT IGNORE INTO tui VALUES (...), ...

INSERT IGNORE INTO interests (name) SELECT interest_name AS name FROM tui

INSERT IGNORE INTO users_interests SELECT users.id AS user_id, interests.id AS interest_id FROM interests JOIN tui ON interests.name=tui.interest_name JOIN users ON users.name='Vasja'

DROP TABLE tui;
COMMIT;