create table users(
    id uuid primary key,
    name varchar(32) not null unique,
    password varchar(128)
);

create table accounts(
    id uuid primary key,
    "user" uuid not null references users(id),
    name varchar(32) not null,
    balance bigint not null default 0 constraint positive_balance check (balance >= 0),
    unique ("user", name)
);

create table transactions(
    id uuid primary key,
    "from" uuid not null references accounts(id),
    "to" uuid not null references accounts(id),
    amount bigint not null constraint positive_amount check (amount > 0),
    timestamp timestamp without time zone not null default now(),
    message text
);

create index transactions_from on transactions ("from");
create index transactions_to on transactions ("to");

create view transactions_with_user as select t.*, (select user from accounts where id = t.from) as from_user, (select user from accounts where id = t.to) as to_user from transactions t;