MySQL多表连接操作

 select * from userinfo ,dapartment where userinfo.part_id = dapartment.id;
      --左连接: 左边全部显示
      select * from userinfo left join dapartment on userinfo.part_id=dapartment.id;
      --右连接:右边的全部显示
      select * from userinfo right join dapartment on userinfo.part_id=dapartment.id;
      --内连接: 将出现null的一行隐藏
      select * from userinfo inner join dapartment on userinfo.part_id = dapartment.id;