I need to load data from a legacy SQL Server database which uses numeric primary keys into a new database with a different schema that uses sequential Guids for primary keys. In the new system the sequential Guids are generated by the application - it uses the Azure SQL db which doesn't support NEWSEQUENTIALID().
For performance reasons and as there is a lot of data restructuring I want to convert using SQL scripts (i.e. loading data directly into SQL and not going via the application) and I am planning to add a new Id column to each legacy table for the Ids and populating the Ids in each legacy table before inserting into the new schema
I found this which helpfully provided this SQL to generate unique sequential Ids which I can use to generate my new Ids
SELECT CAST(CAST(NEWID() AS BINARY(10)) + CAST(GETDATE() AS BINARY(6)) AS UNIQUEIDENTIFIER) UPDATE sometable SET Id = CAST(CAST(NEWID() AS BINARY(10)) + CAST(GETDATE() AS BINARY(6)) AS UNIQUEIDENTIFIER) But I am a confused why the sequential part of the id is at the end of the Guid - wouldn't that cause index fragmentation?
Would it better to change the SQL to this and have the sequential part of the id at the start?
CAST(CAST(GETDATE() AS BINARY(6)) + CAST(NEWID() AS BINARY(10)) AS UNIQUEIDENTIFIER) Thanks in advance for any insights into which is better
