Question

我有这样的表：

Col1 | Col2
AAA  | 1
BBB  | X
AAA  | X
CCC  | 1

我想找到基于Col1的重复项。然后我想留下在Col2中有'X'的行并删除另一行。

我找到了如何找到重复项：

SELECT col1, col2, col3=count(*)
INTO holdkey
FROM t1
GROUP BY col1, col2
HAVING count(*) > 1

但是这个例子进一步说明了如何删除相同的行而不是如何选择一行。

不过，这是mssql2000

Answer 1

这可以很好地利用可更新的CTE和窗口函数：

with todelete as (
      select t1.*, count(*) over (partition by col1) as cnt
      from t1
     )
delete from todelete
    where cnt > 1 and col2 <> 'X';

Answer 2

假设该表名为test，这应该可行。我刚尝试过： - ）

DELETE From test WHERE Col1 IN(
SELECT Col1 FROM test 
GROUP BY Col1
HAVING COUNT(1) > 1)
AND Col2 = '1'

Answer 3

DELETE tbl1 FROM t1 AS tbl1
CROSS APPLY (
    SELECT TOP 1 tbl2.col1 
    FROM t1 AS tbl2
    WHERE tbl1.col1 = tbl2.col1
    GROUP BY tbl2.col1
    HAVING COUNT(*) > 1
) t2
WHERE tbl1.col2 != 'X'

Answer 4

是否存在Col1重复的情况，但实例没有col2 ='x'。如果您遇到这种情况，您将从表中丢失该值。

select col1 
into tmp
from t1 
group by t1 
having count(*)>1;


delete from t1 
where col1 in (select col1 from tmp) 
 and col2<>'X';

Drop table tmp;

查找重复行并删除特定行

4 个答案: