A historical migration script covers changes you've already committed.

You can add a historical migration script using your version control system:

1. In your version control system:

   1. Checkout the revision prior to the changes that required a migration script.
   2. Create a new branch (eg Historical migration).

2. In SQL Source Control, switch to the new branch.
   The working database in SQL Source Control is reverted to the revision selected in step 1a.

3. Make the changes that required a migration script.
4. Create a new migration script.
5. Commit the migration script.
6. In your version control system, merge the new branch into master.

Deploying from the latest revision now executes the new migration script at the correct point.