update vendors
set default_terms_id = 6 where default_terms_id = 4;
update vendors
set default_terms_id = 9 where default_terms_id = 5;

update invoices
set terms_id = 6 where terms_id=4;
update invoices
set terms_id = 9 where terms_id=5;

select * from terms;

delete from terms where terms_id = 4;
delete from terms where terms_id=5;

insert into terms values(6, 'Net due 60 days', 60);
insert into terms values(9, 'Net due 60 days', 90);


alter table invoice
add constraint chk_inv_due_date
check (invoice_due_date = invoice_date +terms.terms_due_days);

select terms_id, invoice_date, invoice_due_date from invoices;