Cause:Cannot delete or update a parent

我的操作:删除一个id=1的一条数据.

test.java

//删除用户信息 @Test public void test5() { SqlSession sqlSession = SqlSessionFactoryUtils.getSessionFactory().openSession(); sqlSession.delete("user.deleteUser", 1); sqlSession.commit(); sqlSession.close(); }

user.xml

<delete id="deleteUser" parameterType="int"> delete from user where id=#{id} </delete>

mybatis_day01数据库下的两张数据表user和order:

user表:

 order表:

 

user表:

 

报错:

org.apache.ibatis.exceptions.PersistenceException: ### Error updating database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot delete or update a parent row: a foreign key constraint fails (`mybatis_day01`.`order`, CONSTRAINT `FK_order_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION) ### The error may involve user.deleteUser-Inline ### The error occurred while setting parameters ### SQL: delete from user where id=? ### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot delete or update a parent

问题:user表的id外键关联order表,当删除的时候数据的时候,就会报Cannot delete or update a parent错.

解决办法: 先关闭外键约束，执行删除操作，然后再开启外键约束

SET foreign_key_checks = 0;  // 先设置外键约束检查关闭   // 删除数据，表或者视图   SET foreign_key_checks = 1; // 开启外键约束检查，以保持表结构完整性