1.在表t_book中删除press_id为“106”图书信息。
DELETE FROM t_book WHERE press_id='106';

2.设置表t_press中的press_id为主键，t_book中的press_id为外键，外键参照主键。删除press_telephone以“0431”开始的出版社的信息。
ALTER TABLE t_press ADD PRIMARY KEY(press_id);
ALTER TABLE t_book ADD CONSTRAINT fk_pressid FOREIGN KEY(press_id) REFERENCES t_press(press_id);
DELETE FROM t_press WHERE press_telephone LIKE '0431%';

3.修改外键与主键的约束方式为restrict，删除press_telephone以“010”开始的出版社的信息。
ALTER TABLE t_book DROP FOREIGN KEY fk_pressid;
ALTER TABLE t_book DROP INDEX fk_pressid;
ALTER TABLE t_book ADD CONSTRAINT fk_pressid FOREIGN KEY(press_id) REFERENCES t_press(press_id) ON DELETE RESTRICT;
DELETE FROM t_press WHERE press_telephone LIKE '010%';

4修改外键与主键的约束方式为set null ,删除press_telephone以“010”开始的出版社的信息。
ALTER TABLE t_book DROP FOREIGN KEY fk_pressid;
ALTER TABLE t_book DROP INDEX fk_pressid;
ALTER TABLE t_book ADD CONSTRAINT fk_pressid FOREIGN KEY(press_id) REFERENCES t_press(press_id) ON DELETE SET NULL;
DELETE FROM t_press WHERE press_telephone LIKE '010%';

5修改外键与主键的约束方式为cascade ,删除press_telephone以“0431”开始的出版社的信息。
ALTER TABLE t_book DROP FOREIGN KEY fk_pressid;
ALTER TABLE t_book DROP INDEX fk_pressid;
ALTER TABLE t_book ADD CONSTRAINT fk_pressid FOREIGN KEY(press_id) REFERENCES t_press(press_id) ON DELETE CASCADE;
DELETE FROM t_press WHERE press_telephone LIKE '0431%';

