Question

假设我有一个包含几亿行的表，看起来像这样：

memID | foo  | bar  | foobar
1     | blah | blah | blah
1     | blah | blah | blah
1     | blah | blah | blah
1     | blah | blah | blah
1     | blah | blah | blah
1     | blah | blah | blah
1     | blah | blah | blah
2     | blah | blah | blah
2     | blah | blah | blah
2     | blah | blah | blah
2     | blah | blah | blah
2     | blah | blah | blah
.
.
.
10001 | blah | blah | blah
10001 | blah | blah | blah

我需要一个查询，它将返回一系列成员ID中每个memID的前N行。例如，如果N = 3且范围为0-2，则应返回

memID | foo  | bar  | foobar
1     | blah | blah | blah
1     | blah | blah | blah
1     | blah | blah | blah
2     | blah | blah | blah
2     | blah | blah | blah
2     | blah | blah | blah

我考虑过几种方法，首先创建一个大规模的

SELECT TOP (3) *
FROM table
WHERE memID = 0
UNION ALL
SELECT TOP (3) *
FROM table
WHERE memID = 1
.
.
.

在代码中查询。出于可能明显的原因，这不是一个真实的选择。

第二种方法是创建一个临时表并循环遍历memID的范围，将每个memID的TOP 3插入到该临时表中。

WHILE @MemID < 10000 AND @MemID > 0
  BEGIN
    INSERT INTO tmp_Table
    SELECT TOP (3) *
     FROM table
     WHERE memID = @MemID

    SET @MemID = @MemID + 1
    END

这有效，但我想知道是否有一个更优雅的单一查询解决方案，我不知道。

Cadaeic给了我一个没有修补的答案，但是感谢所有提出分析的人，看起来我有一些认真的阅读。

Answer 1

declare @startID int, @endID int, @rowsEach int
select @startID = 0, @endID = 2, @rowsEach = 3


select *
from
(
    select memID, foo, bar, foobar, row_number() over (partition by dense_rank order by dense_rank) [rank_row]
    from
    (
        select memID, foo, bar, foobar, dense_rank() over (order by memID) [dense_rank]
        from #test
        where memID between @startID and @endID
    ) a
) b
where rank_row <= @rowsEach

结果：

memID       foo  bar  foobar rank_row
----------- ---- ---- ------ --------------------
1           blah blah blah   1
1           blah blah blah   2
1           blah blah blah   3
2           blah blah blah   1
2           blah blah blah   2
2           blah blah blah   3

如果你想在本地测试，这里是设置代码：

create table #test
(
      memID     int not null
    , foo       char(4) not null
    , bar       char(4) not null
    , foobar    char(4) not null
)

insert into #test (memID, foo, bar, foobar)
select 1, 'blah', 'blah', 'blah'
union all
select 1, 'blah', 'blah', 'blah'
union all
select 1, 'blah', 'blah', 'blah'
union all
select 1, 'blah', 'blah', 'blah'
union all
select 1, 'blah', 'blah', 'blah'
union all
select 1, 'blah', 'blah', 'blah'
union all
select 1, 'blah', 'blah', 'blah'
union all
select 2, 'blah', 'blah', 'blah'
union all
select 2, 'blah', 'blah', 'blah'
union all
select 2, 'blah', 'blah', 'blah'
union all
select 2, 'blah', 'blah', 'blah'
union all
select 10001, 'blah', 'blah', 'blah'
union all
select 10001, 'blah', 'blah', 'blah'
union all
select 10001, 'blah', 'blah', 'blah'

Answer 2

SQL> select ename,sal,
  2   row_number()
  3     over (order by sal desc)rn,
  4   rank()
  5     over (order by sal desc)rnk,
  6   dense_rank()
  7     over (order by sal desc)drnk
  8   from emp
  9  order by sal desc
 10  /

ENAME    SAL   RN   RNK   DRNK
-----   ----   --   ---   ----
 KING   5000    1     1      1
 FORD   3000    2     2      2
SCOTT   3000    3     2      2
JONES   2975    4     4      3
BLAKE   2850    5     5      4
CLARK   2450    6     6      5

Answer 3

如果您使用的是SQL Server 2005或2008，则可能需要调查Ranking Functions

Answer 4

使用分析。我没有测试过，但应该关闭：

SELECT memID, foo, bar, foobar 
FROM  (
       SELECT memID, foo, bar, foobar, 
              RANK() OVER (PARTITION BY memID ORDER BY memID) AS 'nRank'
       FROM   table
       WHERE  memID BETWEEN 0 AND 2)
WHERE  nRank <= 3

Answer 5

SELECT * FROM Member m
Join ( Select TOP(3) * From Table Order By Table.Id) as t 
    On t.MemberId = m.MemberId
Where m BETWEEN 0 and 10000

应该做的伎俩

SQL查询在一系列ID中返回每个ID的前N行

5 个答案: