Database Analytics Loader

def load_user_activities(connection_string: str, user_id: int = None) -> object:
    """
    Load user activity records from the database.

    If user_id is provided, filter activities for that specific user.
    Otherwise, load all user activities.

    Args:
        connection_string: Database connection string
        user_id: Optional user ID to filter activities

    Returns:
        A dataframe containing activity records with columns:
        activity_id, user_id, activity_type, timestamp, duration_seconds
    """
    pass

def load_daily_summary(connection_string: str, start_date: str, end_date: str) -> object:
    """
    Load aggregated daily activity summaries.

    Returns daily totals of activities and total duration for the date range.

    Args:
        connection_string: Database connection string
        start_date: Start date in 'YYYY-MM-DD' format
        end_date: End date in 'YYYY-MM-DD' format

    Returns:
        A dataframe with columns: activity_date, total_activities, total_duration
    """
    pass

def load_multiple_datasets(connection_string: str, queries: list) -> list:
    """
    Load multiple datasets by executing multiple queries.

    Args:
        connection_string: Database connection string
        queries: List of SQL query strings to execute

    Returns:
        List of dataframes, one for each query in the same order
    """
    pass

def load_to_arrow(connection_string: str, query: str) -> object:
    """
    Load query results into Apache Arrow format.

    Args:
        connection_string: Database connection string
        query: SQL query string

    Returns:
        PyArrow Table containing the query results
    """
    pass