学步园

1. 内联查询 select p.ss, dpt.st from products p inner join department dpt on p.type_id=dep.typeid and p.name=dep.name;
                        如果连接字段相同：select p.ss, dpt.st from products p inner join department dpt using(type_id, name);
2. 左连接 select p.ss, pt.st from products p left outer join department using (type_id);
3. 全连接 select p.ss, pt.st from products p full outer join department using (type_id);
4. 笛卡尔 select p.ss, pt.st from products p cross join department ;