mysql - 从父表中选择 if 时，子表中出现奇怪的外键约束冲突

Question

注意:书的 ID 就是书名

insert ignore into category_book 
select 1 as user_id, 'name' as category_name, b.id as book_id 
from book b 
where b.id regexp('word') AND b.id IS NOT NULL

我得到:

MySQL error 1452: Cannot add or update a child row: a foreign key constraint fails (book.category_book, CONSTRAINT fk_category_book_book1 FOREIGN KEY (book_id) REFERENCES book (id) ON DELETE CASCADE ON UPDATE CASCADE)

Answer 1

看起来您正在尝试将一条记录插入到category_book中，而该记录的book_id在表books中不存在。订单 Category_book 列可能与您在选择中提供的列不同。尝试相同的查询，但指示插入子句中的列。