简化嵌套查询

Question

select name 
from person, author, article
where name != "John Doe" AND
      person.pid = author.pid AND
      author.aid = article.aid AND
        title = select title
                from author, person, article
                where person.name = "John Doe" AND
                      author.pid = person.pid AND
                      article.aid = author.aid

以上是我在 sqlite 中为关系代数编写的嵌套查询，该查询输出与 John Doe 合着一篇文章的人的姓名。

这是关系模式：
文章(aid, title, year, confid, numpages) Author(aid, pid) Person(pid, name, affiliation).
我的问题是如何简化嵌套查询？

Answer 1

我完全不明白你的问题与正则表达式有什么关系。不过，如果您想要 co-authored 与 John Doe 的人名，我建议加入：

select distinct pe2.name
from person pe1
inner join author  au1 on au1.pid = pe1.pid
inner join author  au2 on au2.aid = au1.aid and au2.pid <> au1.pid
inner join person  pe2 on pe2.pid = au2.pid
where pe1.name = 'John Doe'

查询从 John Doe 开始，并带入 author 中的相应行；然后，它搜索所有 co-authors，最后找到他们的名字。

简化嵌套查询

Simplify nested queries

mysql

sql

relational-algebra

inner-join

subquery