SQL Pivot Issue - sql

Question

If you could please help with this. The code generates an error:
Msg 8156, Level 16, State 1, Line 236
The column 'Classification_Value_Id' was specified multiple times for 'piv1'.
I am doing this on SQL Server. The steps for the code is as follows:
1. Unpivot the data from the source table DB.[dbo].[Classification] into one column
2. Join this unpivoted data to a table called DB.dbo.[Classification_Value] to return/add the column 'cv.Classification_Name' to the data set
3. Pivot this dataset (This is the part returning the error)
CODE:
SELECT
activityCode
, actjvPartnerRef
, actMonth
, actSalesChannel
, addCBPCharge
, agentId
, appType
, areaCode
--SELECT
--polRef,[Arrangement_Id],UnpivotedData.Classification_Value_Id,UnpivotedData.Classification_Scheme_Id,ColValues, ColNames,cv.Classification_Name
FROM
(
SELECT top 10
[polRef]
, [Arrangement_Id]
, [Classification_Scheme_Id]
, [Classification_Value_Id]
-- ,[Arrangement_Classification_Type_Id]
-- ,[Effective_TimeStamp]
-- ,[End_date]
, CAST((ISNULL([character_measure],'')) AS NVARCHAR(MAX)) AS character_measure
, CAST((ISNULL([datetime_measure],'')) AS NVARCHAR(MAX)) AS datetime_measure
, CAST([decimal_measure] AS NVARCHAR(MAX)) AS decimal_measure
, CAST((ISNULL([integer_measure],'')) AS NVARCHAR(MAX)) AS integer_measure
, CAST((ISNULL([logical_measure],'')) AS NVARCHAR(MAX)) AS logical_measure
, CAST((ISNULL([charmax_measure],'')) AS NVARCHAR(MAX)) AS charmax_measure
, CAST((ISNULL([long_measure],'')) AS NVARCHAR(MAX)) AS long_measure
FROM DB.[dbo].[Classification]
) AS SrcDataConverted
UNPIVOT
(
ColValues FOR ColNames IN
(
character_measure
, datetime_measure
, decimal_measure
, integer_measure
, logical_measure
, charmax_measure
, long_measure
)
) AS UnpivotedData
LEFT JOIN DB.dbo.[Classification_Value] cv
ON cv.[Classification_Scheme_Id] = UnpivotedData.[Classification_Scheme_Id]
AND cv.Classification_Value_Id = UnpivotedData.Classification_Value_Id
PIVOT
(MAX(ColValues) for Classification_Name in (
activityCode
, actjvPartnerRef
, actMonth
, actSalesChannel
, addCBPCharge
, agentId
, appType
, areaCode
)) AS piv1;
Any help would be much appreciated
Thank you

Answer 1

StuarLC:
An additional derived table needs to wrap the results of the UNPIVOT before commencing the re-PIVOT, as the join introduces a duplicated Classification_Value_Id and Classification_Scheme_id, which is needed for the join.
select
activityCode
, actjvPartnerRef
, actMonth
, actSalesChannel
, addCBPCharge
, agentId
, appType
, areaCode
from (
SELECT polRef
, [Arrangement_Id]
, UnpivotedData.Classification_Value_Id
, UnpivotedData.Classification_Scheme_Id
, ColValues
, ColNames
, Classification_Name
FROM (
SELECT [polRef]
, [Arrangement_Id]
, [Classification_Scheme_Id]
, [Classification_Value_Id]
, CAST((ISNULL([character_measure],'')) AS NVARCHAR(MAX)) AS character_measure
, CAST((ISNULL([datetime_measure],'')) AS NVARCHAR(MAX)) AS datetime_measure
, CAST([decimal_measure] AS NVARCHAR(MAX)) AS decimal_measure
, CAST((ISNULL([integer_measure],'')) AS NVARCHAR(MAX)) AS integer_measure
, CAST((ISNULL([logical_measure],'')) AS NVARCHAR(MAX)) AS logical_measure
, CAST((ISNULL([charmax_measure],'')) AS NVARCHAR(MAX)) AS charmax_measure
, CAST((ISNULL([long_measure],'')) AS NVARCHAR(MAX)) AS long_measure
FROM DB.[dbo].[Classification]
) AS SrcDataConverted
UNPIVOT
(
ColValues FOR ColNames IN
(
character_measure
, datetime_measure
, decimal_measure
, integer_measure
, logical_measure
, charmax_measure
, long_measure
)
) AS UnpivotedData
LEFT JOIN
DB.dbo.[Classification_Value] cv
ON cv.[Classification_Scheme_Id] = UnpivotedData.[Classification_Scheme_Id]
AND cv.Classification_Value_Id = UnpivotedData.Classification_Value_Id
) as src
PIVOT
(
MAX(ColValues) for Classification_Name in (
activityCode
, actjvPartnerRef
, actMonth
, actSalesChannel
, addCBPCharge
, agentId
, appType
, areaCode
)
) AS piv1;