如何在SQL中检查下一个值是否接近上一个值

Question

I have a table which has columns

ID int,
NUM int,
FK_POS int,
TRANS_DATE datetime

First of all, I get the rows of this table, then i want to get the next rows's values (by ID), then i want to check if next row's NUM,FK_POS and TRANS_dATE values are the same with the previous rows's value..

For example i have;

"ID" "NUM" "FK_POS" "TRANS_DATE"
"1"  "429" "2043" "2015-01-11 23:40:00.000"

I want to check NUM,FK_POS and TRANS_DATE values of the second row.

And if there is a row like this;

"2"  "429" "2043" "2015-01-11 23:40:00.000"

That's what I want; is this possible?

Answer 1

If you are using SQL Server 2012+, then you can use lead() :

select t.*,
       (case when num = lead(num) over (order by id) and
                  fk_pos = lead(fk_pos) over (order by id) and
                  trans_date = lead(trans_date) over (order by id)
             then 1 else 0
        end) as SameAsNext
from table t;

If you are using an earlier version, you can do something very similar with cross apply :

select t.*,
       (case when t.num = tnext.num and
                  t.fk_pos = tnext.fk_pos and
                  t.trans_date = tnext.rans_date
             then 1 else 0
        end) as SameAsNext
 from table t cross apply
     (select top 1 t2.*
      from table t2
      where t2.id > t.id
      order by t2.id asc
     ) tnext

Answer 2

You can join the table with itself:

SELECT ID, NUM, FK_POS, TRANS_DATE,
       NextRowHasSameValues = CASE 
          WHEN t2.ID IS NOT NULL
           AND t1.NUM = t2.NUM
           AND t1.FK_POS = t2.FK_POS 
           AND t1.TRANS_DATE = t2.TRANS_DATE 
          THEN 'Yes' ELSE 'No' END
FROM dbo.TableName t1
LEFT OUTER JOIN dbo.TablName t2
    ON t1.ID = t2.ID - 1

Answer 3

Something like this?

SELECT *
FROM table a JOIN table b on b.id = a.id + 1
WHERE a.NUM = b.NUM AND etc...

Answer 4

The first way I can think of doing this (there might be a better way) is using a where clause and EXISTS

SELECT ID, NUM, FK_POS, TRANS_DATE
    FROM tblTable pt
        WHERE EXISTS(SELECT 1 FROM tblTable ct WHERE pt.NUM = ct.NUM AND pt.FK_POS = ct.FK_POS AND pt.TRANS_DATE = ct.TRANS_DATE AND pt.ID + 1 = ct.ID)
        /*This is assuming your ID is an Identity field*/

If you don't care if it's the previous row, you can use several better methods:

The first, and probably best, is by using GROUP BY

SELECT MIN(ID)/*or MAX(ID)*/, NUM, FK_POS, TRANS_DATE
    FROM tblTable
        GROUP BY NUM, FK_POS, TRANS_DATE
            HAVING COUNT(*) > 1

Or, you can use DISTINCT with subqueries

SELECT ID, NUM, FK_POS, TRANS_DATE
    FROM tblTable
        WHERE ID NOT IN (SELECT DISTINCT NUM, FK_POS, TRANS_DATE FROM tblTable)