SQL查询从结果集查询中选择最大值和最小值

Question

I've got a stored procedure with a query:

SELECT
    ID
    ,AmountInCurrency
    ,ExtractionDate
FROM
    Table

This query returns 2 rows:

ID  AmountInCurrency    ExtractionDate
1   8.00                2013-10-17 10:00:00.000
1   10.50               2013-09-16 09:00:00.000

I want to select the Min and Max Extrationdate into variables @mindate and @maxdate. Right now I put the resultset into a temp table and select the max and min from that.

But is it possible to do it otherwise like in the select:

ID  AmountInCurrency    ExtractionDate          MinExtractionDate       MaxExtractionDate
1   8.00            2013-10-17 10:00:00.000     2013-09-16 09:00:00.000     2013-10-17 10:00:00.000
1   10.50           2013-09-16 09:00:00.000     2013-09-16 09:00:00.000     2013-10-17 10:00:00.000

Answer 1

It looks like you want to add the min and max date as extra columns in the result set. If so, use the window functions:

SELECT ID, AmountInCurrency, ExtractionDate,
       min(ExtractionDate) over () as MinExtractionDate,
       max(ExtractionDate) over () as MaxExtractionDate
FROM Table;

Answer 2

declare @mindate datetime,
              @maxdate datetime

select @mindate = min(extraction_date),
            @maxdate = max(extraction_date)
from tbl