Sql 在CreatedDate字段的帮助下获取插入的最新行

我正在尝试根据其CreatedDate将最新记录插入SQL表中。例如，在下表中，我想得到第三行

A   B   C   2009-05-04 19:30:52.847
A   B   D   2009-05-04 19:30:55.050
A   B   E   2009-05-04 19:30:57.003

我有一个有效的查询，但我想知道是否有更好的方法来实现相同的结果。下面是我现在用于测试的表、数据和查询。有没有更好的办法

CREATE TABLE TestTable (
  ColumnA     NVARCHAR(10),
  ColumnB     NVARCHAR(10),
  ColumnC     NVARCHAR(10),
  CreatedDate DATETIME    DEFAULT Getutcdate())

INSERT INTO TestTable(ColumnA, ColumnB, ColumnC) VALUES ('A', 'B', 'C');
INSERT INTO TestTable(ColumnA, ColumnB, ColumnC) VALUES ('A', 'B', 'D');
INSERT INTO TestTable(ColumnA, ColumnB, ColumnC) VALUES ('A', 'B', 'E');

SELECT *
FROM   TestTable
WHERE  CreatedDate = (SELECT   Max(CreatedDate)
                      FROM     TestTable
                      WHERE    ColumnA = 'A'
                               AND ColumnB = 'B'
                      GROUP BY ColumnA,
                               ColumnB) 

谢谢

你也可以写

SELECT top 1 *
FROM   TestTable
order by CreatedDate desc

---

给这只猫剥皮有多种方法。有些尚未发布：

SELECT
     T1.column_a,
     T1.column_b,
     T1.column_c,
     T1.created_date
FROM
     dbo.Test_Table T1
WHERE
     T1.column_a = 'A' AND
     T1.column_b = 'B' AND
     NOT EXISTS
     (
          SELECT
               *
          FROM
               dbo.Test_Table T2
          WHERE
               T2.column_a = T1.column_a AND
               T2.column_b = T1.column_b AND
               T2.created_date > T1.created_date
     )

或

---

我喜欢外部连接解决方案-我没有想到。但是显示估计执行计划发现它比我通常解决这个问题的方法更昂贵。（可能与我表格上的索引有关-您的里程数可能会有所不同）请尝试一下：

SELECT
    T1.ColumnA,
    T1.ColumnB,
    T1.ColumnC,
    T1.CreatedDate
FROM
    dbo.TestTable T1
    JOIN (SELECT ColumnA,
                 ColumnB,
                 max(CreatedDate) MaxDate
          FROM
                 dbo.TestTable
          GROUP BY ColumnA,
                   ColumnB) T2
    ON  T1.ColumnA     = T2.ColumnA
    AND T1.ColumnB     = T2.ColumnB
    AND T1.CreatedDate = T2.MaxDate 

这只是为了防止

CreatedDate

中存在重复项，并且您需要所有这些重复项

否则，只需放下带有领带的

SELECT
    T1.ColumnA,
    T1.ColumnB,
    T1.ColumnC,
    T1.CreatedDate
FROM
    dbo.TestTable T1
    JOIN (SELECT ColumnA,
                 ColumnB,
                 max(CreatedDate) MaxDate
          FROM
                 dbo.TestTable
          GROUP BY ColumnA,
                   ColumnB) T2
    ON  T1.ColumnA     = T2.ColumnA
    AND T1.ColumnB     = T2.ColumnB
    AND T1.CreatedDate = T2.MaxDate 

SELECT TOP 1 WITH TIES *
FROM TestTable
WHERE ColumnA = 'A'
  AND ColumnB = 'B'
ORDER BY CreatedDate DESC