What are the primary and foreign keys in these tables? Also, what data constrain

Question

What are the primary and foreign keys in these tables? Also, what data constraints exist from these tables? Thanks

TRAIN (table) TRAIN_ID TRAIN_NAME TRAIN_SCHEDULE (table) TRAIN_ID STATION_ID ARRIVAL_TIME DEPARTURE_TIME TRAIN_SEATS (table) SEAT_ID SEAT_NUMBER TRAIN_ID STATION (table) STATION_ID STATION_NAME STATION_LOCATION PASSENGER (table) PASSENGER_ID PASSENGER_FIRSTNAME PASSENGER_LASTNAME ADDRESS PHONE_NUMBER RESERVATION (table) RESERVATION_ID PASSENGER_ID DATE_OF_TRAVEL STATION_ID SEAT_RESERVATION (table) SEAT_ID RESERVATION_ID

Explanation / Answer

Bellow constraints exist from these tables

not null - each value in a column must not be NULL
unique - value(s) in specified column(s) must be unique for each row in a table
primary key - value(s) in specified column(s) must be unique for each row in a table and not be NULL; normally each table in a database should have a primary key - it is used to identify individual records
foreign key - value(s) in specified column(s) must reference an existing record in another table (via it's primary key or some other unique constraint)

TRAIN (table) TRAIN_ID Primary Key TRAIN_NAME TRAIN_SCHEDULE (table) TRAIN_ID Foreign Key STATION_ID Foreign Key ARRIVAL_TIME DEPARTURE_TIME TRAIN_SEATS (table) SEAT_ID Primary Key SEAT_NUMBER TRAIN_ID Foreign Key STATION (table) STATION_ID Primary Key STATION_NAME STATION_LOCATION PASSENGER (table) PASSENGER_ID Primary Key PASSENGER_FIRSTNAME PASSENGER_LASTNAME ADDRESS PHONE_NUMBER RESERVATION (table) RESERVATION_ID Primary Key PASSENGER_ID Foreign Key DATE_OF_TRAVEL STATION_ID Foreign Key SEAT_RESERVATION (table) SEAT_ID Foreign Key RESERVATION_ID Foreign Key

Bellow constraints exist from these tables

not null - each value in a column must not be NULL
unique - value(s) in specified column(s) must be unique for each row in a table
primary key - value(s) in specified column(s) must be unique for each row in a table and not be NULL; normally each table in a database should have a primary key - it is used to identify individual records
foreign key - value(s) in specified column(s) must reference an existing record in another table (via it's primary key or some other unique constraint)

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