有如下两张关联表
mysql数据库插入两张表
内连接——显示两个表中有联系的所有数据
方式一：select * from unicom.staff inner join unicom.profession where unicom.staff.profession = unicom.profession.profession;
方式二: select * from unicom.staff, unicom.profession where unicom.staff.profession = unicom.profession.profession;
左连接——以左表为参照,显示所有数据,右表中没有则以null显示
select * from unicom.staff left join unicom.profession on unicom.staff.profession = unicom.profession.profession;
右连接——以右表为参照显示数据，,左表中没有则以null显示
select * from unicom.staff right join unicom.profession on unicom.staff.profession = unicom.profession.profession;
