MySQL 5.6

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE tm (
    id INT AUTO_INCREMENT,
    PRIMARY KEY (id)
);
CREATE TABLE th (
    id INT AUTO_INCREMENT,
    PRIMARY KEY (id)
);
CREATE TABLE tr (
    id INT AUTO_INCREMENT,
    tm_id INT,
    th_id INT,
    PRIMARY KEY (id), 
    CONSTRAINT fk_1 FOREIGN KEY (tm_id) REFERENCES tm (id) ON DELETE CASCADE ON UPDATE CASCADE,
    CONSTRAINT fk_2 FOREIGN KEY (th_id) REFERENCES th (id) ON DELETE CASCADE ON UPDATE CASCADE
);
INSERT INTO th (id) VALUES (1);
INSERT INTO tm (id) VALUES (101);
INSERT INTO tm (id) VALUES (102);
INSERT INTO tr (tm_id, th_id) VALUES (101,1), (102,1);
SELECT *
FROM th
LEFT JOIN tr ON tr.th_id = th.id
LEFT JOIN tm ON tr.tm_id = tm.id
WHERE th.id = 1;


id
id
tm_id
th_id
id


1
1
101
1
101

1
2
102
1
102


DELETE th, tr, tm
FROM th
LEFT JOIN tr ON tr.th_id = th.id
LEFT JOIN tm ON tr.tm_id = tm.id
WHERE th.id = 1;
SELECT * FROM th
SELECT * FROM tm


id


102


SELECT * FROM tr