# Функция для замены NULL на пустые строки
def replace_null_with_empty_string(conn):
    cursor = conn.cursor()
    query = """
        UPDATE contacts
        SET 
            name = COALESCE(name, ''),
            phone = COALESCE(phone, ''),
            email = COALESCE(email, '')
    """
    cursor.execute(query)
    conn.commit()