ID:	credit	promise debt
--------------------------------
Club:	0	+7200	-23450
john:	7200	+0	-7200
# Reflect john paying its bills all at once ...
Club:	7200	+0	-23450
john:	0	+0	0
# Charge Club with server hosting provided by alex ...
Club:	0	+0	-16250
alex:	7200	+16250	0
# Some updates and deletes that could, unless denied, destroy consistency ...
Error: near line 409: paid is set and adjusted automatically according to added Transfer records
Error: near line 410: Debt is involved in transfers to revoke at first
Error: near line 411: FOREIGN KEY constraint failed
# After revoking transactions, you are free to change or delete debts and credits ...
Club:	7200	+0	0
alex:	0	+0	0
# But let's rollback that what-if excurse. This is how it currently is ...
Club:	0	+0	-16250
alex:	7200	+16250	0
###################################################################
# Now it is your turn: Study the sql code yielding the output above
# then enter new members and let them pay the fees.
# (PLUS: Let have one discalculia and pay too little or too much.)
# Once the club has enough money to pay alex' hosting service,
# update (i.e. revoke and reenter) the respective transaction.
# Finally issue a bank transfer to alex. Hint: An outgoing transfer
# is simply a debt charging alex' own virtual account and without
# targetCredit (NULL). PLUS: What happens if the description of
# the bank transfer does not contain any or only a wrong IBAN?