求详细分析一下这段SQL语句
$sql=mysql_query("select * from (select bookid,count(bookid) as degree from tb_borrow group by bookid) as borr join (select b.*,c.name as bookcasename,p.pubname,t.typename from tb_bookinfo b left join tb_bookcase c on b.bookcase=c.id join tb_publishing p on b.ISBN=p.ISBN join tb_booktype t on b.typeid=t.id where b.del=0) as book on borr.bookid=book.id order by borr.degree desc limit 10")
求详细分析一下这段SQL语句
select *
from (
select bookid, count(bookid) as degree
from tb_borrow
group by bookid
) as borr
join (
select b.*,c.name as bookcasename,p.pubname,t.typename
from tb_bookinfo b
left join tb_bookcase c on b.bookcase=c.id
join tb_publishing p on b.ISBN=p.ISBN
join tb_booktype t on b.typeid=t.id
where b.del=0
) as book on borr.bookid=book.id
order by borr.degree desc limit 10
s155336
11 years, 10 months ago
Answers
这条语句其实获取的就是借调（tb_borrow ）最多的10本书的所有所有信息。
下面的语句意思是：通过按组统计方式获取每本书的借调数（count(bookid)）
下面语句的意思是：获取没有被删除的书的信息，包括主信息tb_bookinfo，tb_bookcase ，出版方 tb_publishing， 以及书本类型信息tb_booktype
select b.*,c.name as bookcasename,p.pubname,t.typename
from tb_bookinfo b
left join tb_bookcase c on b.bookcase=c.id
join tb_publishing p on b.ISBN=p.ISBN
join tb_booktype t on b.typeid=t.id
where b.del=0
通过以上转换就成了
popopo
answered 11 years, 10 months ago