sql-server - 如何从 SQL Server 中的表中删除重复的行

Question

我有一个名为的表table1，其中包含重复的值。它看起来像这样：

new
pen
book
pen
like
book
book
pen

但我想从该表中删除重复的行并将它们插入另一个名为table2.

table2应该是这样的：

new 
pen
book
like

如何在 SQL Server 中执行此操作？

Answer 1

您可以使用您使用INSERT的SELECTs轻松完成此操作，例如：CTEROW_NUMBER()

DECLARE @YourTable table (YourColumn varchar(10))
DECLARE @YourTable2 table (YourColumn varchar(10))
INSERT INTO @YourTable VALUES ('new')
INSERT INTO @YourTable VALUES ('pen')
INSERT INTO @YourTable VALUES ('book')
INSERT INTO @YourTable VALUES ('pen')
INSERT INTO @YourTable VALUES ('like')
INSERT INTO @YourTable VALUES ('book')
INSERT INTO @YourTable VALUES ('book')
INSERT INTO @YourTable VALUES ('pen')

;WITH OrderedResults AS
(
SELECT
    YourColumn, ROW_NUMBER() OVER (PARTITION BY YourColumn ORDER BY YourColumn) AS RowNumber
    FROM @YourTable
)
INSERT INTO @YourTable2 
        (YourColumn)
    SELECT YourColumn FROM OrderedResults
        WHERE RowNumber=1

从@YourTable2 中选择 *

输出：

YourColumn
----------
book
like
new
pen

(4 row(s) affected)

您可以在您使用DELETE的地方轻松地做到这一点，例如：CTEROW_NUMBER()

--this will just remove them from your original table
DECLARE @YourTable table (YourColumn varchar(10))
INSERT INTO @YourTable VALUES ('new')
INSERT INTO @YourTable VALUES ('pen')
INSERT INTO @YourTable VALUES ('book')
INSERT INTO @YourTable VALUES ('pen')
INSERT INTO @YourTable VALUES ('like')
INSERT INTO @YourTable VALUES ('book')
INSERT INTO @YourTable VALUES ('book')
INSERT INTO @YourTable VALUES ('pen')

;WITH OrderedResults AS
(
SELECT
    YourColumn, ROW_NUMBER() OVER (PARTITION BY YourColumn ORDER BY YourColumn) AS RowNumber
    FROM @YourTable
)
DELETE OrderedResults
    WHERE RowNumber!=1

SELECT * FROM @YourTable

输出：

YourColumn
----------
new
pen
book
like

(4 row(s) affected)

Answer 2

假设该字段名为name：

INSERT INTO table2 (name)
SELECT name FROM table1 GROUP BY name

该查询将为您提供所有唯一名称。

如果需要，您甚至可以将它们放入表变量中：

DECLARE @Table2 TABLE (name VARCHAR(50))

INSERT INTO @Table2 (name)
SELECT name FROM table1 GROUP BY name

或者您可以使用临时表：

CREATE TABLE #Table2 (name VARCHAR(50))

INSERT INTO @Table2 (name)
SELECT name FROM table1 GROUP BY name

Answer 3

几周前，我使用 DELETE TOP X 发布了一些关于删除重复项的内容。显然，仅针对一组重复项。然而，在评论中，Joshua Patchak 给了我这颗小宝石。

;WITH cte(rowNumber) AS
(SELECT ROW_NUMBER() OVER (PARTITION BY [List of Natural Key Fields] 
ORDER BY [List of Order By Fields]) 
FROM dbo.TableName)

DELETE FROM cte WHERE rowNumber>1

这将消除表中的所有重复项。
如果您想阅读讨论，这是原始帖子。表中的重复行。