Here is a sample relational schema design for a travel booking system

CUSTOMER (customer_id PK, name, email, phone)

BOOKING (booking_id PK, customer_id FK, trip_id FK

          booking_date, booking_status, number_of_passengers, total_price )  

TRIP ( trip_id PK, destination_id FK, accommodation_id FK, 

          departure_date,  return_date, trip_name, description, itinerary )  

DESTINATION ( destination_id PK, country, city, region)

ACCOMMODATION (accommodation_id PK, hotel_name, address, room_type, star_rating )

PAYMENT (payment_id PK, booking_id FK, payment_date, float amount, payment_method)

PK = Primary Key, FK = Foreign Key

Write SQL Statements for following use-cases:

1.  List all customers who have booked travel to 'London' 

2.  List destinations with 4-star accommodations

3.  List customers who have booked their travel using payment method "Credit Card" and whose amount is more than 100,000