print("\n--- DEFAULT value check for Sydney ---")
sydney = pd.read_sql("""SELECT City_Name, Country, Is_Capital
    FROM City
    WHERE City_Name == 'Sydney';""", conn)
print(sydney)
print("Is_Capital was not given — DEFAULT 'No' was used automatically.")


print("\n--- NULL in the Population column ---")
all_cities = pd.read_sql("""SELECT City_Name, Country, Population
    FROM City;""", conn)
print(all_cities)

missing = pd.read_sql("""SELECT City_Name FROM City
    WHERE Population IS NULL;""", conn)
print("Cities with no population data:")
print(missing)

has_data = pd.read_sql("""SELECT City_Name, Population FROM City
    WHERE Population IS NOT NULL;""", conn)
print("Cities with population data:")
print(has_data)

conn.close()