Question

我正在尝试将列值与同一个表中之前的后续行列值进行比较。我在网上看到了一些解决方案但无法满足我的需求。

ALTER PROCEDURE [dbo].[compare_results_by_id] 
    @history_id int
AS
BEGIN
--declare table to insert old value and new value
declare @HistoryLog table (ColumnName varchar(100), OldValue varchar(max), NewValue varchar(max), updated_by int)

declare @previousID int

    SELECT [history_id]
          ,[first_name]
          ,[last_name]
          ,[occupation]
          ,[updated_by]
      FROM History_Table where history_id = @history_id

-- get previous row 

    SELECT @previousID  = P.PreviousID
    FROM
    (SELECT  MAX(D.history_id) PreviousID
    FROM History_Table D
    WHERE informant_history_id < @history_id) P

-- TODO Compare results
END

如何循环并比较两行的列值？有没有更好的方法？请告诉我。

Answer 1

SELECT c.history_id, max(p.history_id)
  FROM History_Table c
  LEFT JOIN History_Table p
        on p.history_id < c.history_id 
 GROUP BY c.history_id;

你可能想要使用带有rn的cte

with cte as  
(  SELECT [history_id]
        , [first_name]
        , [last_name]
        , [occupation]
        , [updated_by]
        , row_number() over (order by [history_id] ) as rn  ) 
select c.*, n.*    
  from cte as c    
  left join cte as p 
         on c.rn = n.rn-1;

比较并列出与同一表

1 个答案: