SQL数据库中两个表A,B存放内容不一样，需要关联两表查询数据．

问题1：E机构里面的每个名称下面有多少个价格，如果要制定某一个名称，可以在where条件中增加name最为条件:
select a.name , count(price) from a,b where a.mediid = b.mediid and a.forgid = b.forgid and a.forgid = 'E' group by a.name;
如果要去掉重复价格可以增加distinct，如下：
select a.name , count(distinct price) from a,b where a.mediid = b.mediid and a.forgid = b.forgid and a.forgid = 'E' group by a.name;
问题2：查询E机构下面，两个表中编号相同的项目
select count(name) from a,b where a.mediid = b.mediid and a.forgid = b.forgid and a.forgid = 'E';

select name,count(*) from a,b where a.moduleid=b.moduleid
and a.forgid='E' group by name

你要是不建主键多少个都可以有