Mysql 如何查询具有3个不同表的SQL数据库，其中包含有关参与者、角色和执行的角色的信息？

数据库包含有关参与者、角色和执行的角色的信息

Actor(actor_id, name, year_born) 
Play(play_id, title, author, year_written) 
Role(actor_id, character_name, play_id)

为什么这些尝试是错误的

要做：

SQL查询，返回1980年出生并在5部以上戏剧中演出的演员的姓名。 2.SQL查询，返回在作者“Arthur Miller”编写的所有剧本中扮演的演员的姓名

我对问题1的尝试

Select DISTINCT a.name
From Actor a , Role r , Play p
Where a.year_born = 1980
HAVING count(DISTINCT r.play_id) > 5

我对问题2的尝试

SELECT DISTINCT a.name
From Actor a , Role r , Play p
Where p.author = “Arthur Miller” AND p.play_id=r.play_id and r.actor_id = a.actor_id
HAVING count (DISTINCT a.actor_id = p.play_id)

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在这两个查询中，您都缺少GROUPBY子句。而且，由于您在选择列表中使用的是GROUPBY distinct关键字，所以不需要

问题1：

  Select a.name
    From Actor a inner join  Role r on a.actor_id=r.actor_id
    Where a.year_born = 1980
    Group by a.name
    HAVING count(DISTINCT r.play_id) > 5

问题2：

SELECT a.name
From Actor a inner join Role r 
on r.actor_id = a.actor_id
inner join Play p
on p.play_id=r.play_id 
Where p.author = 'Arthur Miller' 
group by a.name
HAVING count (distinct p.play_id) =(select count(*) from Play where author = 'Arthur Miller' )

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你必须先加入表格

例如： 注意*由于角色表包含actor_id和play_id，因此我将角色表作为基表

select a.name
from role as r
inner join actor as a On a.actor_id = r.actor_id
inner join play as p On r.play_id = p.play_id
where p.author = "Arthur Miller”