Create INSERT script with incrementing ID for linked tables (SQL server) - sql

Question

I have a regular task which involves exporting two tables from one database and importing the data into another database whose corresponding tables are not empty. One of the tables in question has a column which refers to the ID of the first. Let's call them Customer and Customer_Address where Customer_Address has a column Cust_ID referring to ID in the Customer table.
I need to create an import script for these which will add the Customer records to the other, non-empty DB with ID = max(id)+1 for each row while not breaking the link to the other table. The Customer_Address table likewise has its own ID column which needs to be incremented in the same manner.
I don't strictly need to have the first inserted record be one higher than the existing highest ID, but it would be best. I've managed in the past to manually check the highest ID in the target DB and add this number using search and replace and a variable in the import script but it's laborious and fails if any records are added to the target DB in the interim.
I have another method which involves selecting, copying, pasting and SQL-wrapping selected all columns but ID from the source tables using Excel and using select(max) instead of the ID but again it's rather tedious.
Edit with data:
Sample script to create source and destination tables (in the same/temdb database for convenience) is here:
http://pastebin.com/C64wFtsP
Should give output as follows:
select * from customer
id Last First
1 Johnson James
2 Kelly Karl
3 Lawlor Liam
select * from customer2
id Last First
1 Adams Ann
2 Byrne Bressie
3 Casey Charlene
select * from customeraddress
id idclient street city county country
1 1 65 North St. Marcoussin Jojoba Flatland
2 2 42 South St. Marcoussin Jojoba Flatland
3 3 12 West St. Marcoussin Jojoba Flatland
4 1 17 East St. Marcoussin Jojoba Flatland
5 1 75 Centre St. Marcoussin Jojoba Flatland
select * from customeraddress2
id idclient street city county country
1 1 99 North St. Marcoussin Jojoba Flatland
2 2 88 South St. Marcoussin Jojoba Flatland
3 3 88 West St. Marcoussin Jojoba Flatland
4 1 66 East St. Marcoussin Jojoba Flatland
5 1 55 Centre St. Marcoussin Jojoba Flatland
What I'm looking for is a way to script an import of the data in both source tables to the corresponding destination tables, while preserving the link between the idclient in customeraddress and the id in customer.

Answer 1

If you can stage data in your destination database, just do this:
Stage both tables in Destination, all fields.
Insert users into new Destination table.
Write a query like this
Note that you'll need to identify a natural key for your customers (the thing that makes them distinct entities in Customer1 that also exists in Customer2) - firstName, lastName probably isn't the best as they're highly unlikely to be distinct across your customer base, but it's what you've got in your sample data.
INSERT INTO customeraddress2
SELECT
customer2.id,
staged_customeraddress1.street,
staged_customeraddress1.city,
staged_customeraddress1.county,
staged_customeraddress1.country
FROM customer2
JOIN staged_customer1
ON staged_customer1.firstName = customer2.firstName
AND staged_customer1.lastName = customer2.lastName
JOIN staged_customeraddress1
ON staged_customeraddress1.idclient = staged_customer1.id