Seed the autoincrement differently for each office?

e.g.

1 for head office

100,000,001 for 1st branch

200,000,001 for 2nd branch

....

2,000,000,001 for 20th branch

if you need more rows/branches than can be accomodated with int (including -ve int seeds), try bigint.

//or//

Use creatorid & id as composite primary key (and composite foreign key in related tables).

Chris