Question

我想执行一个选择请求，然后执行第一次选择，然后使用该选择来执行第二次选择。

我使用临时表制作了第一个版本，但我想知道是否有一种方法可以在没有临时表的情况下完成

我的临时表代码如下：

select  dvd_name, book_name  , count(*) nb
into #t
from usr 
inner join book on usr_book_id  = book_id 
inner join dvd on dvd_id = usr_dvd_id
group by dvd_name, book_name 
having count(*) > 1

select  top 10 usr_smthg,  #t.book_name,dvd_name
from #t
inner join book b on b.book_name = #t.book_name
inner join usr on usr_book_id  = book_id

Answer 1

您可以为此使用CTE

with t as
(
    select  dvd_name, book_name  , count(*) nb
    from usr 
    inner join book on usr_book_id  = book_id 
    inner join dvd on dvd_id = usr_dvd_id
    group by dvd_name, book_name 
    having count(*) > 1
)

select  top 10 usr_smthg,  t.book_name,dvd_name
from t
inner join book b on b.book_name = t.book_name
inner join usr on usr_book_id  = book_id

Answer 2

在sql中，您可以使用子查询，如下所示：

select  top 10 usr.usr_smthg,  t.book_name, usr.dvd_name
from (
  select  dvd_name, book_name  , count(*) nb
  from usr 
  inner join book on usr_book_id  = book_id 
  inner join dvd on dvd_id = usr_dvd_id
  group by dvd_name, book_name 
  having count(*) > 1
) t
inner join book b on b.book_name = t.book_name
inner join usr on usr_book_id  = book_id 
-- guess
order by n.nb desc

Answer 3

您可以将窗口函数与子查询一起使用：

select top (10) t.usr_smthg, t.book_name, t.dvd_name
from (select usr_smthg, book_name, dvd_name, 
             count(*) over (partition by dvd_name, book_name) as cnt
      from usr inner join 
           book 
           on usr_book_id  = book_id inner join 
           dvd 
           on dvd_id = usr_dvd_id
     ) t
 where cnt > 1 
 order by ??;

??表示基于您想要的top (10)记录的排序列。

SQL从选择查询中选择

3 个答案: