Question

我正在尝试编写一个查询，如果在更改值之前删除了“重复”值。例如，我有以下数据：

id, date_recived, name1, percent
1, 8/19/13, Joe, 2
2, 8/15/13, Joe, 3
3, 8/12/13, Joe, 2
4, 4/08/13, Joe, 2

在此示例中，我只需删除ID为3的行，因为百分比没有变化。我尝试过使用Row_Number，但是当我按名称进行分区时，数据显示如下：

id, date_recived, name1, percent, Row_Number
1, 8/19/13, Joe, 2, 3
2, 8/15/13, Joe, 3, 1
3, 8/12/13, Joe, 2, 2
4, 4/08/13, Joe, 2, 1

这不起作用，因为1会被抛出，我需要保留它。任何帮助将不胜感激。

谢谢，

编辑：

查询是（来自评论）：

WITH feedback_On_Same_Date AS (
      SELECT id, received_dt, participant_nm, pretax_deferral_prcnt,
             ROW_NUMBER() OVER(PARTITION BY participant_nm, received_dt ORDER BY received_dt DESC, id DESC) AS RowNumberByDt
      FROM be_ing_feedback
     )
SELECT *, ROW_NUMBER() OVER(PARTITION BY participant_nm, pretax_deferral_prcnt ORDER BY received_dt ASC, id ASC) AS RowNumberByDef
FROM feedback_On_Same_Date
WHERE RowNumberByDt = 1
ORDER BY participant_nm ASC, received_dt DESC

Answer 1

听起来你想要删除“前一个”相同的行。

为此，我将使用Row_Number（）函数和自连接：

; WITH cte AS (
  SELECT id
       , date_recived
       , name1
       , percent
       , Row_Number() OVER (PARTITION BY name ORDER BY date_recived) As seq
  FROM   your_table
)
SELECT *
FROM   cte As curr
 LEFT
  JOIN cte As prev
    ON prev.name1   = curr.name1
   AND prev.seq + 1 = curr.seq

查看此查询返回的数据，然后只需添加WHERE子句即可获取要删除的记录。

我会将其余部分留给您;-)

Answer 2

如果您使用的是SQL Server 2012，请使用lag()功能：

select id, date_recived, name1, percent
from (select t.*,
             lag(percent) over (partition by name1 order by date_received) as prev_percent
      from t
     ) t
where percent <> prev_percent or prev_percent is null;

从SQL查询中删除“重复”记录

2 个答案: