Question[SQL]: How can I list all book with prices greather than the average price of books of the same type?

Question: How can I list all book with prices greather than the average price of books of the same type?
In database pubs, have a table named titles , its column named price mean the price of the book, and another named type mean the type of books.
Now I want to get the result as below:

 程序代码
type         title                                                                            price                
------------ -------------------------------------------------------------------------------- ---------------------
business     The Busy Executive's Database Guide                                              19.9900
…
…
…

…

 

Answer:

select  a. [ type ] , a. [ title ] , a. [ price ]
     from   [ pubs ] . [ dbo ] . [ titles ]  a,
    ( select   [ type ] ,  [ price ] = AVG ( [ price ] )  from   [ pubs ] . [ dbo ] . [ titles ]   group   by   [ type ] ) b
     where  a. [ type ] = b. [ type ]   and  a. [ price ] > b. [ price ]

 

这里还有一个类拟的试题：

第一题比较简单，查询出销售表中，销售额大于本地区平均水平的记录，用一条sql语句就搞定了。

Sales表

OrderID	Region	Total
1	A	100.00
2	C	80.00
3	A	130.00
4	B	90.00
5	B	100.00
6	C	120.00
7	A	90.00
8	C	90.00
9	B	80.00

Sql语句：

select   *   from  sales  as  s 
   inner   join  
   ( select   avg (total)  as  avge,region  from  sales  group   by  region) avgtable 
   on  s.region  =  avgtable.region 
   where  total  >  avgtable.avge