-- 004_balance_constraints.sql
-- Enforce balance integrity constraints
-- WARNING: Apply after data cleanup if you have existing inconsistent data

ALTER TABLE bank_accounts
  ADD CONSTRAINT bank_accounts_reserved_nonnegative
  CHECK (reserved_balance >= 0);

ALTER TABLE bank_accounts
  ADD CONSTRAINT bank_accounts_available_nonnegative
  CHECK (available_balance >= 0);

ALTER TABLE bank_accounts
  ADD CONSTRAINT bank_accounts_balance_consistency
  CHECK (
    available_balance <= balance
    AND (available_balance + reserved_balance) <= balance
  );