仅选择数据的最后部分

Question

我有以下数据

我希望结果如下：

对于阿尔巴尼亚，我想为阿尔巴尼亚的City_Code（此处为20008）的最后一个值选择日期的最小值和最大值（20008的最小值为18.01.2013，20008的最大值为20.01） 0.2013）。对于克罗地亚，City_Code的最后一个值是'零'，所以我们不应该选择任何东西（如果'City_Code'的最后一个值为零，则根本不选择它）。对于斯洛文尼亚，City_Code的最后一个值是70005，因此我们选择相应日期的最小值和最大值（此处最大值和最小值为22.01.2013）。代码应该如何？我什么都不知道。提前致谢

Answer 1

试试这个......

;
WITH    cte_countries ( Country, City_code, CurrentDate, LatestRank )
          AS ( SELECT   Country ,
                        City_code ,
                        CurrentDate ,
                        RANK() OVER ( PARTITION BY country ORDER BY CurrentDate DESC ) AS LatestRank
               FROM     @countries
               WHERE City_code != 0
             )
    SELECT  *
    FROM    cte_countries
    WHERE   LatestRank = 1

Answer 2

SELECT Country,
       max(City_code),
       min(DATE),
       max(Date)
FROM T as T1
WHERE City_code = (SELECT TOP 1 City_Code 
                          FROM T WHERE T.Country=T1.Country 
                          ORDER BY Date DESC)
GROUP BY Country
HAVING max(City_Code)<>'0'

Answer 3

试试这个：

With Cities
AS (
    select Country, City_Code, Min([Date]) Date1, Max([Date]) Date2, 
           ROW_NUMBER() OVER(PARTITION BY Country ORDER BY Country, City_Code DESC) Seq
    from MyCountryCityTable t
    group by t.Country, t.City_Code
)
Select
    Country,
    NULLIF(City_Code,0) City_Code,
    CASE WHEN City_Code = 0 THEN NULL ELSE Date1 END Date1,
    CASE WHEN City_Code = 0 THEN NULL ELSE Date2 END Date2
From Cities Where Seq = 1
Order by Country

修改

没有公用表表达式的版本（WITH）：

Select
    Country,
    NULLIF(City_Code,0) City_Code,
    CASE WHEN City_Code = 0 THEN NULL ELSE Date1 END Date1,
    CASE WHEN City_Code = 0 THEN NULL ELSE Date2 END Date2
From (select Country, City_Code, Min([Date]) Date1, Max([Date]) Date2, 
           ROW_NUMBER() OVER(PARTITION BY Country ORDER BY Country, City_Code DESC) Seq
    from MyCountryCityTable t
    group by t.Country, t.City_Code) Cities 
Where Seq = 1
Order by Country