Question

I have an old database that is a single flat table. I want to copy the old data to the new db structure. Both are MSSQL databases. Here’s a simplified example of what I want to do:

OLD_DB                                     New_DB

Customers_Table             Customers_Table         Phone_Numbers
---------------             --------------          -------------  
FirstName                   CustomerID              PhoneNumberID
LastName          -->       FirstName               CustomerID
PhoneNumber1                LastName                PhoneNumber
PhoneNumber2
PhoneNumber3

I understand how to copy the flat data. This seems to work just fine:

INSERT INTO   New_DB.dbo.Customers_Table (FirstName, LastName)
SELECT        FirstName, LastName
FROM          OLD_DB.dbo.Customers_Table

I just don’t know how to get the phone numbers into the new structure.

Answer 1

If your FirstName and LastName are your unique identifiers, you can run this using UNION after you run your above statement:

INSERT INTO New_DB.dbo.Phone_Numbers (CustomerId, PhoneNumber)
SELECT C.CustomerID, OldC.PhoneNumber1
FROM New_DB.dbo.Customers_Table C
  JOIN OLD_DB.dbo.Customers_Table OldC ON C.FirstName = OldC.FirstName 
     AND C.LastName = OldC.LastName 
     AND OldC.PhoneNumber1 IS NOT NULL
UNION
SELECT C.CustomerID, OldC.PhoneNumber2
FROM New_DB.dbo.Customers_Table C
  JOIN OLD_DB.dbo.Customers_Table OldC ON C.FirstName = OldC.FirstName 
     AND C.LastName = OldC.LastName 
     AND OldC.PhoneNumber2 IS NOT NULL
UNION
SELECT C.CustomerID, OldC.PhoneNumber3
FROM New_DB.dbo.Customers_Table C
  JOIN OLD_DB.dbo.Customers_Table OldC ON C.FirstName = OldC.FirstName 
     AND C.LastName = OldC.LastName 
     AND OldC.PhoneNumber3 IS NOT NULL

Alternatively, you could use UNPIVOT and run something like this (I’ve condensed it for testing, but same concept):

SELECT Id, Phone 
FROM ( SELECT id, phone1, phone2, phone3 FROM Phone ) p
UNPIVOT
(Phone FOR Phones IN (phone1, phone2, phone3))AS Phone

Here is the SQL Fiddle for the UNPIVOT:

Good luck.