连库时，外键异常，请指教

Question

Cannot add or update a child row: a foreign key constraint fails (ldb.pet, CONSTRAINT master_id FOREIGN KEY (master_id) REFERENCES master (id))
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (ldb.pet, CONSTRAINT master_id FOREIGN KEY (master_id) REFERENCES master (id))

Answer 1

    外键异常，外键一般对应另一个表的主键，对外键值更新时，要确保另一个表的主键有存在该值，否则插入报错，违反主键约束