Question

I need to merge data from 2 tables into a third (all having the same schema) and generate a mapping of old identity values to new ones. The obvious approach is to loop through the source tables using a cursor, inserting the old and new identity values along the way. Is there a better (possibly set-oriented) way to do this?

UPDATE: One additional bit of info: the destination table already has data.

Answer 1

Create your mapping table with an IDENTITY column for the new ID. Insert from your source tables into this table, creating your mapping.

SET IDENTITY_INSERT ON for your target table.

Insert into the target table from your source tables joined to the mapping table, then SET IDENTITY_INSERT OFF.