有没有办法将选择查询的结果分成相等的两半？

Question

我需要 Sql Server 2005 中的选择查询解决方案。

我想要一个返回两个 ResultSet 的查询，每个 ResultSet 恰好包含符合特定条件的所有记录的一半。我尝试将 TOP 50 PERCENT 与 Order By 结合使用，但如果表中的记录数为奇数，则两个结果集中都会显示一条记录。我不想在记录集上复制任何记录。示例：

我有一个简单的表，其中包含 TheID (PK) 和 TheValue 字段 (varchar(10)) 以及 5 条记录。现在跳过 where 子句。

SELECT TOP 50 PERCENT * FROM TheTable ORDER BY TheID asc

产生所选 id 的 1,2,3

SELECT TOP 50 PERCENT * FROM TheTable ORDER BY TheID desc

产生所选 id 的 3,4,5

3 是一个重复。当然，在现实生活中，查询相当复杂，包含大量 where 子句和子查询。

Answer 1

SQL Server 2005 和类似版本：

select *, ntile(2) over(order by theid) as tile_nr from thetable

ntile(n) 将输出分配到 n 个段中，每个段的大小相同（当行数不能被 n 整除时，进行舍入或舍入）。所以这会产生输出：

1 | value1 | 1
2 | value2 | 1
3 | value3 | 1
4 | value4 | 2
5 | value5 | 2

如果只需要上半部分或下半部分，则需要将其放入子查询中，例如：

select theid, thevalue from (
  select theid, thevalue, ntile(2) over(order by theid) as tile_nr from thetable
) x
where x.tile_nr = 1

将返回上半部分，同样使用x.tile_nr = 2 作为下半部分

Answer 2

您可以使用这两个查询：

SELECT * FROM (
    SELECT *, ROW_NUMBER() OVER (ORDER BY TheID) AS rn FROM TheTable
) T1
WHERE rn % 2 = 0

SELECT * FROM (
    SELECT *, ROW_NUMBER() OVER (ORDER BY TheID) AS rn FROM TheTable
) T1
WHERE rn % 2 = 1

Answer 3

如果这是 SQL Server 2000，那么我倾向于像这样找到中间值的 PK：

Declare @MiddleId int

Set @MiddleId = (
                Select TOP 1 PK
                From (
                        Select TOP 50 PERCENT PK
                        From Table
                        Order By TheId ASC
                        )
                Order By TheId DESC
                )

Select ...
From Table
Where TheId <= @MiddleId

Select ..
From Table
Where TheId > @MiddleId

对于 SQL Server 2005，我倾向于这样做，但您可以使用 CTE

;With NumProjects As
    (
    Select Id, ROW_NUMBER() OVER (ORDER BY TheId ASC ) As Num
    From Table
    )
Select @MiddleId = Id
From Table
Where Num = CEILING( (Select Count(*) From Table) / 2 )

Answer 4

试试这个：

DECLARE @CountOf int,@Top int,@Bottom int
SELECT @CountOf=COUNT(*) FROM YourTable
SET @Top=@CountOf/2
SET @Bottom=@CountOf-@Top
SELECT TOP (@Top) * FROM YourTable ORDER BY 1 asc --assumes column 1 is your PK
SELECT TOP (@Bottom) * FROM YourTable ORDER BY 1 desc --assumes column 1 is your PK

Answer 5

这是另一个解决方案：

您需要使用临时表来保存前 50%，如下所示：

select top 50 percent * 
into #YourTempTable
from TheTable 

-- The below would give the first half
select * from #YourTempTable

-- The below woud give rest of the half 
select * from TheTable where TheID not in (select TheID from #YourTempTable)

Answer 6

这是the query 我觉得很有用（当然修改后）：

DECLARE @numberofitemsperpage INT DECLARE @numberofpages INT DECLARE @currentpage int

DECLARE @countRecords float SET @countRecords = (Select COUNT(*) From sz_hold_visitsData) -- Excel 一次可以保存大约一百万条记录。如果@countRecords >= 1000000 SET @numberofitemsperpage = 500000 ELSE IF @countRecords = 500000 设置 @numberofitemsperpage = 250000 ELSE IF @countRecords = 100000 设置 @numberofitemsperpage = 50000 其他设置 @numberofitemsperpage = 10000

DECLARE @numberofpages_deci float SET @numberofpages_deci = @countRecords / @numberofitemsperpage

SET @numberofpages = CEILING(@numberofpages_deci) 选择 @countRecords AS countRecords, @numberofitemsperpage AS numberofitemsperpage , @numberofpages_deci AS numberofpages_deci, @numberofpages AS numberofpagesFnl

SET @currentpage =0 WHILE @currentpage = @currentpage * @numberofitemsperpage +1 AND Row

如果@@ROWCOUNT = 0 BREAK SET @currentpage = @currentpage +1 END

在此摘录中，“sz_hold_visitsData”是我数据库中的一个表，而“person_ID”是其中的一个列。 您还可以进一步修改脚本以输出到文件：

声明 @numberofitemsperpage INT DECLARE @numberofpages INT DECLARE @currentpage int

DECLARE @countRecords float SET @countRecords = (Select COUNT(*) From sz_hold_visitsData) -- Excel 一次可以保存大约一百万条记录。如果@countRecords >= 1000000 SET @numberofitemsperpage = 500000 ELSE IF @countRecords = 500000 设置 @numberofitemsperpage = 250000 ELSE IF @countRecords = 100000 设置 @numberofitemsperpage = 50000 其他设置 @numberofitemsperpage = 10000

DECLARE @numberofpages_deci float SET @numberofpages_deci = @countRecords / @numberofitemsperpage

SET @numberofpages = CEILING(@numberofpages_deci) 选择 @countRecords AS countRecords, @numberofitemsperpage AS numberofitemsperpage , @numberofpages_deci AS numberofpages_deci, @numberofpages AS numberofpagesFnl

DECLARE @sevrName nvarchar(50) SET @sevrName = '.\sql14' 声明 @outputFile nvarchar(500)

SET @currentpage =0 WHILE @currentpage = @currentpage * @numberofitemsperpage +1 AND Row

声明@cmd_varchar(500) = 'sqlcmd -S' + @sevrName + ' -E -Q "SELECT a.* FROM (SELECT row_number() OVER (ORDER BY person_ID) AS ROW, * FROM sz_hold_visitsData) WHERE ROW >= '+ CONVERT(nvarchar(500),@currentpage * @numberofitemsperpage +1) +' AND 行

如果@@ROWCOUNT = 0 BREAK SET @currentpage = @currentpage +1 END

希望有所帮助。