alter table {schema}.activities
    add column if not exists price_category text not null default 'h',
    add column if not exists default_sales_price numeric(14, 4);

alter table {schema}.activities
    drop constraint if exists activities_price_category_valid;

alter table {schema}.activities
    add constraint activities_price_category_valid check (price_category in ('h', 'tag', 'pauschal'));

alter table {schema}.activities
    drop constraint if exists activities_default_sales_price_non_negative;

alter table {schema}.activities
    add constraint activities_default_sales_price_non_negative check (
        default_sales_price is null or default_sales_price >= 0
    );