快速和脏删除精确重复的行(小表):

select  distinct * into t2 from t1;
delete from t1;
insert into t1 select *  from t2;
drop table t2;

在postgresql中删除重复行的一个非常简单的方法。

DELETE FROM table1 a
USING table1 b
WHERE a.id < b.id
AND a.column1 = b.column1
AND a.column2 = b.column2;

从应用程序级别(不幸的是)。我同意防止重复的正确方法是在数据库级别上使用唯一的索引，但是在SQL Server 2005中，一个索引只能是900字节，而我的varchar(2048)字段打破了这一规定。

我不知道它的性能如何，但我认为您可以编写一个触发器来强制执行这一点，即使您不能直接使用索引。喜欢的东西:

-- given a table stories(story_id int not null primary key, story varchar(max) not null)
CREATE TRIGGER prevent_plagiarism 
ON stories 
after INSERT, UPDATE 
AS 
    DECLARE @cnt AS INT 

    SELECT @cnt = Count(*) 
    FROM   stories 
           INNER JOIN inserted 
                   ON ( stories.story = inserted.story 
                        AND stories.story_id != inserted.story_id ) 

    IF @cnt > 0 
      BEGIN 
          RAISERROR('plagiarism detected',16,1) 

          ROLLBACK TRANSACTION 
      END 

另外，varchar(2048)对我来说听起来很可疑(生活中有些东西是2048字节，但这很少见);它真的应该不是varchar(max)吗?

我更喜欢CTE从sql server表中删除重复的行

强烈推荐阅读本文::http://codaffection.com/sql-server-article/delete-duplicate-rows-in-sql-server/

保持原创性

WITH CTE AS
(
SELECT *,ROW_NUMBER() OVER (PARTITION BY col1,col2,col3 ORDER BY col1,col2,col3) AS RN
FROM MyTable
)

DELETE FROM CTE WHERE RN<>1

不保留原创

WITH CTE AS
(SELECT *,R=RANK() OVER (ORDER BY col1,col2,col3)
FROM MyTable)
 
DELETE CTE
WHERE R IN (SELECT R FROM CTE GROUP BY R HAVING COUNT(*)>1)

通过使用下面的查询，我们可以基于单列或多列删除重复的记录。下面的查询是基于两列进行删除。表名为:testing，列名为empno,empname

DELETE FROM testing WHERE empno not IN (SELECT empno FROM (SELECT empno, ROW_NUMBER() OVER (PARTITION BY empno ORDER BY empno) 
AS [ItemNumber] FROM testing) a WHERE ItemNumber > 1)
or empname not in
(select empname from (select empname,row_number() over(PARTITION BY empno ORDER BY empno) 
AS [ItemNumber] FROM testing) a WHERE ItemNumber > 1)

DELETE LU 
FROM   (SELECT *, 
               Row_number() 
                 OVER ( 
                   partition BY col1, col1, col3 
                   ORDER BY rowid DESC) [Row] 
        FROM   mytable) LU 
WHERE  [row] > 1