从表中删除重复记录

Question

我有一个名为Table1的表,它有48条记录.其中只有24个应该在那个表中.出于某种原因,我插入了重复的记录.如何从该表中删除重复记录.

Answer 1

如果SQL Server版本是2005或更高版本,您可以尝试以下内容.

WITH cte AS
    (
    SELECT {list-of-columns-in-table},
      row_number() over (PARTITION BY {list-of-key-columns} ORDER BY {rule-to-determine-row-to-keep}) as sequence
    FROM myTable
    )

DELETE FROM cte
WHERE sequence > 1

这使用公用表表达式(CTE)并添加序列列.{list-of-columns-in-table}就像它所说的那样.并非所有列都是必需的,但我不会在此解释.

{list-of-key-columns]是用于定义重复内容的列.

{rule-to-determination-row-to-keep}是一个序列,因此第一行是要保留的行.例如,如果要保留最旧的行,则可以使用日期列作为序列.

这是使用真实列的查询示例.

WITH cte AS
    (
    SELECT ID, CourseName, DateAdded,
        row_number() over (PARTITION BY CourseName ORDER BY DateAdded) as sequence
    FROM Courses
    )

DELETE FROM cte
WHERE sequence > 1

此示例根据CoursName值删除重复的行,并将最旧的行保留在DateAdded值上.