mysql - 如何删除SQL Server中的重复行？(How to delete duplicate rows in SQL Server?)

Question

How can I delete duplicate rows where no unique row id exists?

(如何删除不存在unique row id 重复行 ？)

My table is

(我的桌子是)

col1  col2 col3 col4 col5 col6 col7
john  1    1    1    1    1    1 
john  1    1    1    1    1    1
sally 2    2    2    2    2    2
sally 2    2    2    2    2    2

I want to be left with the following after the duplicate removal:

(在重复删除后，我想保留以下内容：)

john  1    1    1    1    1    1
sally 2    2    2    2    2    2

I've tried a few queries but I think they depend on having a row id as I don't get the desired result.

(我已经尝试了一些查询，但是我认为它们依赖于行ID，因为我没有得到期望的结果。)

For example:

(例如：)

DELETE
FROM table
WHERE col1 IN (
    SELECT id
    FROM table
    GROUP BY id
    HAVING (COUNT(col1) > 1)
)

  ask by Fearghal translate from so

Answer 1

I like CTEs and ROW_NUMBER as the two combined allow us to see which rows are deleted (or updated), therefore just change the DELETE FROM CTE... to SELECT * FROM CTE :

(我喜欢CTE和ROW_NUMBER因为两者结合使我们能够看到删除（或更新）了哪些行，因此只需将DELETE FROM CTE...更改为SELECT * FROM CTE ：)

WITH CTE AS(
   SELECT [col1], [col2], [col3], [col4], [col5], [col6], [col7],
       RN = ROW_NUMBER()OVER(PARTITION BY col1 ORDER BY col1)
   FROM dbo.Table1
)
DELETE FROM CTE WHERE RN > 1

DEMO (result is different; I assume that it's due to a typo on your part)

(演示 （结果有所不同；我认为这是由于您的错字引起的）)

COL1    COL2    COL3    COL4    COL5    COL6    COL7
john    1        1       1       1       1       1
sally   2        2       2       2       2       2

This example determines duplicates by a single column col1 because of the PARTITION BY col1 .

(由于PARTITION BY col1本示例通过单个列col1确定重复项。)

If you want to include multiple columns simply add them to the PARTITION BY :

(如果要包括多个列，只需将它们添加到PARTITION BY ：)

ROW_NUMBER()OVER(PARTITION BY Col1, Col2, ... ORDER BY OrderColumn)