Incorrect syntax near the keyword 'PRIMARY' :   <code>  USE db_Airline;

CREATE TABLE AIRPORT (
    Airport_code NVARCHAR(10) PRIMARY KEY,
    Name NVARCHAR(25) NOT NULL,
    City NVARCHAR(25) NOT NULL,
    State NVARCHAR(25) NOT NULL 
);

CREATE TABLE FLIGHT (
    Flight_number NVARCHAR(15) PRIMARY KEY,
    Airline NVARCHAR(25) NOT NULL,
    Weekdays INTEGER DEFAULT 0
);

CREATE TABLE FLIGHT_LEG (
    Flight_number NVARCHAR(15) NOT NULL,
    Leg_number INTEGER NOT NULL,
    Departure_airport_code NVARCHAR(10) NOT NULL,
    Scheduled_departure_time TIME NOT NULL,
    Arrival_airport_code NVARCHAR(10) NOT NULL,
    Scheduled_arrival_time TIME NOT NULL,
    CONSTRAINT PRIMARY KEY 
        Pk_Flight_Leg (Flight_number, Leg_number),
    CONSTRAINT FOREIGN KEY 
        Fk_Flight_Leg_Flight (Flight_number)
    REFERENCES
        FLIGHT (Flight_number)
    ON UPDATE CASCADE ON DELETE CASCADE
);

CREATE TABLE FARE (
    Flight_number NVARCHAR(15) NOT NULL,
    Fare_code NVARCHAR(15) NOT NULL,
    Amount DECIMAL(10,2) NOT NULL,
    Restrictions NVARCHAR(50),
    CONSTRAINT PRIMARY KEY
        Pk_Fare (Flight_number, Fare_code),
    CONSTRAINT FOREIGN KEY
        Fk_Fare_Flight (Flight_number)
    REFERENCES
        FLIGHT (Flight_number)
    ON UPDATE CASCADE ON DELETE CASCADE
);

CREATE TABLE AIRPLANE_TYPE (
    Airplane_type_name NVARCHAR(25) PRIMARY KEY,
    Max_seats INTEGER NOT NULL,
    Company NVARCHAR(25)
);

CREATE TABLE AIRPLANE (
    Airplane_id NVARCHAR(25) PRIMARY KEY,
    Total_number_of_seats INTEGER NOT NULL,
    Airplane_type NVARCHAR(25) NOT NULL,
    CONSTRAINT FOREIGN KEY
        Fk_Airplane_Airplane_Type (Airplane_type)
    REFERENCES
        AIRPLANE_TYPE (Airplane_type_name)
    ON UPDATE CASCADE ON DELETE CASCADE
);

CREATE TABLE LEG_INSTANCE (
    Flight_number NVARCHAR(15) NOT NULL,
    Leg_number INTEGER NOT NULL,
    Leg_instance_date Date NOT NULL,
    Number_of_available_seats INTEGER,
    Airplane_id NVARCHAR(25) NOT NULL,
    Departure_airport_code NVARCHAR(10) NOT NULL,
    Departure_time TIME NOT NULL,
    Arrival_airport_code NVARCHAR(10) NOT NULL,
    Arrival_time TIME NOT NULL,
    CONSTRAINT PRIMARY KEY
        Pk_Leg_Instance (Flight_number, Leg_number, Leg_instance_date),
    CONSTRAINT FOREIGN KEY
        Fk_Leg_Instance_Flight_Leg (Flight_number, Leg_number)
    REFERENCES
        FLIGHT_LEG (Flight_number, Leg_number)
    ON UPDATE CASCADE ON DELETE CASCADE,
    CONSTRAINT FOREIGN KEY
        Fk_Leg_Instance_Airplane (Airplane_id)
    REFERENCES
        AIRPLANE (Airplane_id)
    ON UPDATE CASCADE ON DELETE CASCADE
);

CREATE TABLE CAN_LAND (
    Airplane_type_name NVARCHAR(25) NOT NULL,
    Airport_code NVARCHAR(10) NOT NULL,
    CONSTRAINT PRIMARY KEY
        Pk_Can_Land (Airplane_type_name, Airport_code),
    CONSTRAINT FOREIGN KEY
        Fk_Can_Land_Airplane_Type (Airplane_type_name)
    REFERENCES
        AIRPLANE_TYPE (Airplane_type_name)
    ON UPDATE CASCADE ON DELETE CASCADE,
    CONSTRAINT FOREIGN KEY
        Fk_Can_Land_Airport (Airport_code)
    REFERENCES
        AIRPORT (Airport_code)
    ON UPDATE CASCADE ON DELETE CASCADE
);

CREATE TABLE SEAT_RESERVATION (
    Flight_number NVARCHAR(15) NOT NULL,
    Leg_number INTEGER NOT NULL,
    Leg_instance_date Date NOT NULL,
    Seat_number INTEGER NOT NULL,
    Customer_name NVARCHAR(50) NOT NULL,
    Customer_phone NVARCHAR(20),
    CONSTRAINT PRIMARY KEY
        Pk_Seat_Reservation (Flight_number, Leg_number, Leg_instance_date, Seat_number),
    CONSTRAINT FOREIGN KEY
        Fk_Seat_Reservation_Leg_Instance (Flight_number, Leg_number, Leg_instance_date)
    REFERENCES
        LEG_INSTANCE (Flight_number, Leg_number, Leg_instance_date)        
);
</code> 



> Msg 156, Level 15, State 1, Line 23
Incorrect syntax near the keyword 'PRIMARY'.
Msg 156, Level 15, State 1, Line 37
Incorrect syntax near the keyword 'PRIMARY'.
Msg 156, Level 15, State 1, Line 56
Incorrect syntax near the keyword 'FOREIGN'.
Msg 156, Level 15, State 1, Line 73
Incorrect syntax near the keyword 'PRIMARY'.
Msg 156, Level 15, State 1, Line 90
Incorrect syntax near the keyword 'PRIMARY'.
Msg 156, Level 15, State 1, Line 111
Incorrect syntax near the keyword 'PRIMARY'.
