mybatis 使用MySql 简单编写 无需主外键 左外连接多表删除 数据、级联更新数据

   1.无主外键级联删除，主表（tb_userinfo）用户表 

<!--删除用户那么与之用户相关联的所有信息都将被删除。根据用户的unionid删除所有相关数据  -->
    <delete id="deleteUserinfoByid">
     DELETE 
         tb_userinfo,
		 tb_attention,
		 tb_building,
		 tb_code,
		 tb_collection,
		 tb_information,
		 tb_recommend,
		 tb_records,
		 tb_forum
     FROM
	     tb_userinfo
		 LEFT JOIN tb_attention ON (tb_userinfo.unionid = tb_attention.unionids)
		 LEFT JOIN tb_building ON (tb_userinfo.account = tb_building.account)
		 LEFT JOIN tb_code ON (tb_userinfo.unionid = tb_code.unionid)
		 LEFT JOIN tb_collection ON (tb_userinfo.unionid = tb_collection.unionid OR tb_building.id = tb_collection.bid)
		 LEFT JOIN tb_information ON (tb_userinfo.unionid = tb_information.unionid)
		 LEFT JOIN tb_recommend ON (tb_userinfo.unionid = tb_recommend.unionid)
		 LEFT JOIN tb_records ON (tb_userinfo.unionid = tb_records.unionid)
		 LEFT JOIN tb_forum ON (tb_userinfo.unionid = tb_forum.unionid)
    WHERE
	     tb_userinfo.unionid = #{unionid}<!--条件，传入的参数 -->
    </delete>

2，无主外键级联更新，主表（tb_userinfo）用户表

 UPDATE tb_userinfo u
		LEFT JOIN tb_borrow b ON (u.id = b.bid)<!-- 关联条件为用户ID -->
		LEFT JOIN tb_borrow o ON (u.id = o.leid)
		LEFT JOIN tb_credit c ON (u.id = c.userid)
		LEFT JOIN tb_friend f ON (u.id = f.bid)
		LEFT JOIN tb_receipt r ON (u.id = r.userid)
	 SET u.username = #{username},<!--用户名 -->
		 b.borrower = u.username,
		 b.identitycard=u.identitycard,
		 o.lender = u.username,
		 o.identitycards=u.identitycard,
		 c.username=u.username,
		 f.username=u.username,
		 r.username=u.username
	 WHERE
	       u.id = #{id}<!-- 根据用户id -->