Separate Potential Duplicates Into Different Rows

Question

I am trying to identify potential duplicate customers in my database based on the last 4 of the SSN, last name and DOB. The stored procedure I have written does identify potential duplicates but it lists them in one row - I am trying to split into separate rows for reporting reasons.

My T-SQL looks like:

DECLARE
@StartDate DATE = '1/1/2017',
@EndDate DATE = '3/1/2017';

SELECT  DENSE_RANK() OVER (ORDER BY c.socialSecurityNumber) AS [SSNRanking] ,
    ROW_NUMBER() OVER (PARTITION BY c.socialSecurityNumber ORDER BY c.socialSecurityNumber) AS [RowNumb] ,
    c.socialSecurityNumber AS [SSN], 
    c.id AS [CustomerID]  , 
    c.firstName AS [FirstName] ,    
    c.lastName AS [lastName] ,
    c.birthDate [birthdate] ,
    c.createDate AS [CreateDate] ,
    c2.socialSecurityNumber AS [DupSSN] ,
    c2.id AS [DupCustomerID] ,
    c2.firstName AS [DupFirstName] ,
    c2.lastName AS [DupLastName] ,
    c2.birthDate AS [DupBirthDate] ,
    c2.createDate AS [DupCreateDate]
FROM    dbo.Customers AS [c]
    INNER JOIN dbo.Customers AS [c2] ON ( SUBSTRING(c.socialSecurityNumber,6,4) = SUBSTRING(c2.socialSecurityNumber,6,4) AND c.birthDate = c2.birthDate AND c.lastName = c2.lastName AND c.id <> c2.id )
    LEFT JOIN dbo.CustomerAddresses AS [CA] ON c.id = CA.customerID             
    LEFT OUTER JOIN dbo.Common_Orders AS [co] ON co.customerID = c.id
WHERE
    c.customerStatusTypeID <> 'M'
    AND C2.customerStatusTypeID <> 'M'
    AND c.mergedTo IS NULL
    AND c2.mergedTo IS NULL
    AND CAST(co.orderDate AS DATE) >= @StartDate
    AND CAST(co.orderDate AS DATE) <= @EndDate
    AND c.id = 1234439
GROUP BY c.socialSecurityNumber ,
    c.id ,
    c.firstName ,
    c.lastName ,
    c.birthDate ,       
    c.createDate ,
    c2.socialSecurityNumber ,
    c2.id ,
    c2.firstName ,        
    c2.lastName ,
    c2.birthDate ,
    c2.createDate
ORDER BY CAST(c.socialSecurityNumber AS INT) ASC;

And my data set looks like:

SSNRanking  RowNumb  SSN        CustomerID  FirstName  lastName  birthdate  CreateDate  DupSSN     DupCustomerID  DupFirstName  DupLastName  DupBirthDate  DupCreateDate
1           1        000009915  1234439     GREG       GARRETT  1900-01-01  2014-02-25  000009915  1166084        ADAM          GARRETT      1900-01-01    2013-08-29

In this particular instance, I have two users with the same last 4 of the SSN, same last name and same DOB - but different first names.

How can I make these two records appear on separate lines? Ideally, I would like to see:

SSNRanking  RowNumb  SSN        CustomerID  FirstName  lastName  birthdate   CreateDate
1           1        000009915  1234439     GREG       GARRETT   1900-01-01  2014-02-25
1           2        000009915  1166084     ADAM       GARRETT   1900-01-01  2013-08-29 

But I am not sure how I can accomplish this when joining to the same table. Suggestions?

I'm linking to a script that creates the two tables in question and inserts sample data. Hopefully that is acceptable: SQL Script

Answer 1

This is called "unpivot". You can use UNPIVOT operator, but I prefer to use CROSS APPLY ... VALUES.

I'll wrap your query into CTE without looking at it in details and split each row into two using CROSS APPLY.

DECLARE
@StartDate DATE = '1/1/2017',
@EndDate DATE = '3/1/2017';

WITH
CTE
AS
(
    SELECT  
        DENSE_RANK() OVER (ORDER BY c.socialSecurityNumber) AS [SSNRanking] ,
        ROW_NUMBER() OVER (PARTITION BY c.socialSecurityNumber ORDER BY c.socialSecurityNumber) AS [RowNumb] ,
        c.socialSecurityNumber AS [SSN], 
        c.id AS [CustomerID]  , 
        c.firstName AS [FirstName] ,    
        c.lastName AS [lastName] ,
        c.birthDate [birthdate] ,
        c.createDate AS [CreateDate] ,
        c2.socialSecurityNumber AS [DupSSN] ,
        c2.id AS [DupCustomerID] ,
        c2.firstName AS [DupFirstName] ,
        c2.lastName AS [DupLastName] ,
        c2.birthDate AS [DupBirthDate] ,
        c2.createDate AS [DupCreateDate]
    FROM    
        dbo.Customers AS [c]
        INNER JOIN dbo.Customers AS [c2] ON ( SUBSTRING(c.socialSecurityNumber,6,4) = SUBSTRING(c2.socialSecurityNumber,6,4) AND c.birthDate = c2.birthDate AND c.lastName = c2.lastName AND c.id <> c2.id )
        LEFT JOIN dbo.CustomerAddresses AS [CA] ON c.id = CA.customerID             
        LEFT JOIN dbo.Common_Orders AS [co] ON co.customerID = c.id
    WHERE
        c.customerStatusTypeID <> 'M'
        AND C2.customerStatusTypeID <> 'M'
        AND c.mergedTo IS NULL
        AND c2.mergedTo IS NULL
        AND CAST(co.orderDate AS DATE) >= @StartDate
        AND CAST(co.orderDate AS DATE) <= @EndDate
        AND c.id = 1234439
    GROUP BY
        c.socialSecurityNumber ,
        c.id ,
        c.firstName ,
        c.lastName ,
        c.birthDate ,       
        c.createDate ,
        c2.socialSecurityNumber ,
        c2.id ,
        c2.firstName ,        
        c2.lastName ,
        c2.birthDate ,
        c2.createDate
)
SELECT
    CA.SSNRanking
    ,CA.RowNumb
    ,CA.SSN
    ,CA.CustomerID
    ,CA.FirstName
    ,CA.lastName
    ,CA.birthdate
    ,CA.CreateDate
FROM
    CTE
    CROSS APPLY
    (
        VALUES
        (CTE.SSNRanking, CTE.RowNumb, CTE.SSN, CTE.CustomerID, CTE.FirstName, CTE.lastName, CTE.birthdate, CTE.CreateDate),
        (CTE.SSNRanking, CTE.RowNumb, CTE.DupSSN, CTE.DupCustomerID, CTE.DupFirstName, CTE.DuplastName, CTE.Dupbirthdate, CTE.DupCreateDate)
    ) AS CA(SSNRanking, RowNumb, SSN, CustomerID, FirstName, lastName, birthdate, CreateDate)
ORDER BY CAST(CA.SSN AS INT) ASC;

By the way,

ROW_NUMBER() OVER (PARTITION BY ColumnA ORDER BY ColumnA)

doesn't make sense when you partition and order by the same column. I'm not sure what you want to achieve there.