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Editorial Team
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Asked: 2026-06-18T11:52:12+00:00

I’m using a SQL statement to compare consecutive values of a field [Allocation] as

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I’m using a SQL statement to compare consecutive values of a field [Allocation] as follows:

;WITH cteMain AS
(SELECT AllocID, CaseNo, FeeEarner, Allocation, ROW_NUMBER() OVER (ORDER BY AllocID) AS sn
FROM tblAllocations)

SELECT m.AllocID, m.CaseNo, m.FeeEarner, m.Allocation, 
       ISNULL(sLag.Allocation, 0) AS prevAllocation,
      (m.Allocation - ISNULL(sLag.Allocation, 0)) AS movement
FROM cteMain AS m

LEFT OUTER JOIN cteMain AS sLag
ON sLag.sn = m.sn-1;

The query returns a calculated field [movement] which is the increase or decrease in consecutive values of [Allocation].

I have included a screen shot of the data returned by this query.

Screenshot of returned data

However the query is not yet complete. I need to revise the statement so that the consecutive values of [Allocation] compared are grouped / partitioned by [FeeEarner] and [CaseNo].

For example, at line 18 of the data, the [Allocation] is 800 and is compared to a previous value of 600. But the previous value belongs to a different [CaseNo] i.e. 6 rather than 31. In fact [FeeEarner] ‘PJW’ has no previous [Allocation] on [CaseNo] ’31’ and so the [prevAllocation] should be ‘0’ from the ISNULL keyword.

I have tried changing

OVER (ORDER BY AllocID)

to

OVER (PARTITION BY CaseNo, FeeEarner ORDER BY AllocID)

But that results in a lot of lines of data being repeated.

Can someone advise how to compare consecutive values of [Allocation] but only between rows of data with matching [FeeEarner] AND [CaseNo] please?

NOTE – I cannot use LAG because my customer is using SQL Server 2008 R2 which does not support Parallel Data Warehousing.

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1 Answer

  1. Editorial Team

    I believe you were close. Try this (notice the added pieces in the join clause to match the partition – without this you will match every row number 3 with every row number 2 across partitions, which is what you were seeing):

    ;WITH cteMain AS
(
    SELECT AllocID, CaseNo, FeeEarner, Allocation, 
        ROW_NUMBER() OVER (PARTITION BY CaseNo, FeeEarner ORDER BY AllocID) AS sn
    FROM tblAllocations
)    
SELECT m.AllocID, m.CaseNo, m.FeeEarner, m.Allocation, 
       ISNULL(sLag.Allocation, 0) AS prevAllocation,
      (m.Allocation - ISNULL(sLag.Allocation, 0)) AS movement
FROM cteMain AS m

LEFT OUTER JOIN cteMain AS sLag
    ON sLag.CaseNo = m.CaseNo
    AND sLag.FeeEarner = m.FeeEarner
    AND sLag.sn = m.sn-1
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