如何选择SQL

Question

基于LastCreatedDate互不相同的名字我有列示例表：

ID(guid)         Name  CreatedDate 

B27EB95B-B219-46BD-9E72-A378B3E7FED0 A  2005-11-20 22:49:46.000 
33D43825-918D-4DC0-874A-53670563EA03 A  2009-10-03 10:34:00.000 
28F26DA6-B144-4C0C-AC2F-4DDD2D74357E B  2011-03-23 08:08:39.000 
1491D95F-BA58-41EE-8982-B713DE9DECD7 C  2006-01-18 14:53:12.000 
FD25C05D-0C1A-4314-BCA7-F4F33B0E890D C  2006-10-05 14:25:58.000 
F4256300-CAA6-4E80-8D1B-B89273274088 D  2008-03-12 08:56:32.000 

这应该是我在SSIS OledbDatasource。

现在的问题是我需要得到不同的名称具有最后createdDate和它在sql中的Id。

这是输出结果：（变更表表中的实际名称）

ID(guid)         Name  CreatedDate 

33D43825-918D-4DC0-874A-53670563EA03 A  2009-10-03 10:34:00.000 
28F26DA6-B144-4C0C-AC2F-4DDD2D74357E B  2011-03-23 08:08:39.000 
047ED9C3-DF92-45D5-B295-EE52184116FB C   2006-10-05 14:23:40.000 
F4256300-CAA6-4E80-8D1B-B89273274088 D  2008-03-12 08:56:32.000 

谢谢问候

Answer 1

SELECT ID, Name, CreatedDate 
FROM table JOIN 
    (SELECT MAX(CreatedDate) CreatedDate, Name FROM table GROUP BY Name) max_date 
USING (Name, CreatedDate) 

对于SQLServer的事：

SELECT table.ID, table.Name, table.CreatedDate 
FROM table JOIN 
    (SELECT MAX(CreatedDate) CreatedDate, Name FROM table GROUP BY Name) max_date 
ON table.Name = max_date.name AND table.CreatedDate = max_date.CreatedDate 

Answer 2

如果你的SQL Server 2005或更高版本，可以使用ranking和CTE：

WITH ranked AS (
    SELECT 
    ID, Name, CreatedDate, 
    rn = ROW_NUMBER() OVER (PARTITION BY Name ORDER BY CreatedDate DESC) 
    FROM atable 
) 
SELECT 
    ID, 
    Name, 
    CreatedDate 
FROM ranked 
WHERE rn = 1 

Answer 3

这将产生你想要SQL Server上的结果：

select distinct x.ID, x.Name, x.CreatedDate 
from table t 
    cross apply (
     select top 1 ID, Name, CreatedDate 
     from table t1 
     where t1.Name = t.Name 
     order by CreatedDate desc 
    ) x 
order by x.Name; 

Answer 4

尝试了这一点

SELECT myTable.Id, myTable.Name, myTable.CreatedDate 
FROM table as myTable 
INNER JOIN (SELECT Name, MAX(CreatedDate) AS MaxDate FROM table GROUP BY Name) 
    AS MaxRecord ON MaxRecord.Name = myTable.Name 
       AND MaxRecord.MaxDate= myTable.CreatedDate