SQL Assessment: Monthly Bookings Count

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1. Find clients who have met each other

Task 11:

Calculate the count of bookings for each month in 2017. Output a table with columns for month (in 'YYYY-MM' format) and count. Include a total row at the bottom.

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Use PostgreSQL syntax to write your answer. Descriptions of tables are provided at the bottom of the screen.

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Bookings Database (PostgreSQL)

The subject area of this database is airline flights through various airports. The Bookings Database contains 8 tables.

ER diagram of the Bookings database

The list of tables:

aircrafts_data - table of aircrafts.

aircraft_codeUnique code for each aircraft
modelAircraft model name in English and Russian in JSON format
rangeAircraft fly range in kilometers

PRIMARY KEY, btree (aircraft_code)

	aircraft_code	model	range
1	773	{"en": "Boeing 777-300", "ru": "Боинг 777-300"}	11100

airports_data - table of airports.

airport_codeUnique code for each airport
airport_nameAirport name in English and Russian in JSON format
cityAirport city in English and Russian in JSON format
coordinatesAirport coordinates as POINT(longitude, latitude)
timezoneAirport timezone name

PRIMARY KEY, btree (airport_code)

	airport_code	airport_name	city	coordinates	timezone
1	YKS	{"en": "Yakutsk Airport", "ru": "Якутск"}	{"en": "Yakutsk", "ru": "Якутск"}	(129.77099609375,62.0932998657227)	Asia/Yakutsk

boarding_passes - table of boarding passes.

ticket_noTicket number
flight_idFlight identificator
boarding_noBoarding pass number
seat_noSeat number

PRIMARY KEY, btree (ticket_no, flight_id)
UNIQUE CONSTRAINT, btree (flight_id, boarding_no)
UNIQUE CONSTRAINT, btree (flight_id, seat_no)

FOREIGN KEY (ticket_no, flight_id) REFERENCES ticket_flights(ticket_no, flight_id)

	ticket_no	flight_id	boarding_no	seat_no
1	0005435212351	30625	1	2D

bookings - table of bookings.

book_refBooking number
book_dateBooking date
total_amountTotal booking cost

PRIMARY KEY, btree (book_ref)

	book_ref	book_date	total_amount
1	00000F	2017-07-05 00:12:00+00	265700.00

flights - table of flights.

flight_idFlight ID
flight_noFlight number
scheduled_departureScheduled departure time
scheduled_arrivalScheduled arrival time
departure_airportAirport of departure
arrival_airportAirport of arrival
statusFlight status
aircraft_codeAircraft code, IATA
actual_departureActual departure time
actual_arrivalActual arrival time

PRIMARY KEY, btree (flight_id)
UNIQUE CONSTRAINT, btree (flight_no, scheduled_departure)

	flight_id	flight_no	scheduled_departure	scheduled_arrival	departure_airport	arrival_airport	status	aircraft_code	actual_departure	actual_arrival
1	1185	PG0134	2017-09-10 06:50:00+00	2017-09-10 11:55:00+00	DME	BTK	Scheduled	319

seats - table of aircraft seats.

aircraft_codeAircraft code, IATA
seat_noSeat number
fare_conditionsTravel class

PRIMARY KEY, btree (aircraft_code, seat_no)

FOREIGN KEY (aircraft_code) REFERENCES aircrafts(aircraft_code) ON DELETE CASCADE

	aircraft_code	seat_no	fare_conditions
1	319	2A	Business

ticket_flights - ticket to flights relations.

ticket_noTicket number
flight_idFlight ID
fare_conditionsTravel class
amountTravel cost

PRIMARY KEY, btree (ticket_no, flight_id)

FOREIGN KEY (flight_id) REFERENCES flights(flight_id)
FOREIGN KEY (ticket_no) REFERENCES tickets(ticket_no)

	ticket_no	flight_id	fare_conditions	amount
1	0005432159776	30625	Business	42100.00

tickets - table of tickets.

ticket_noTicket number
book_refBooking number
passenger_idPassenger ID
passenger_namePassenger name
contact_dataPassenger contact information

	ticket_no	book_ref	passenger_id	passenger_name	contact_data
1	0005432000987	06B046	8149 604011	VALERIY TIKHONOV	{"phone": "+70127117011"}

PRIMARY KEY, btree (ticket_no)

FOREIGN KEY (book_ref) REFERENCES bookings(book_ref)

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