Postgres 12

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create table users (
    id bigserial primary key,
    username text not null unique,
    email text not null unique,
    first_name text not null,
    last_name text not null
);

create table meals (
    id bigserial primary key,
    type text not null unique,
    -- If calories vary by user, move this into user_meals.
    calories integer not null
);

create table locations (
    id bigserial primary key,
    -- The specific information you have about a location will vary.
    address text,
    city text,
    province text,
    country text,
    postal_code text
);

create table user_meals (
    id bigserial primary key,
    user_id bigint not null references users(id),
    meal_id bigint not null references meals(id),
    location_id bigint not null references locations(id),
    -- Using a time range is more flexible than start + duration.
    taken_at tstzrange not null,
    -- This can store up to 99999.99 which seems reasonable.
    cost numeric(7, 2) not null,
    notes text,
    -- When was this entry created?
    created_at timestamp not null default current_timestamp,
    -- When was it last updated?
    updated_at timestamp not null default current_timestamp
);