CREATE TABLE Invoice (
order_id INT NOT NULL PRIMARY KEY,
branch_id INT,
staff_id INT,
time_id INT,
item_id INT,
payment_id INT,
unit_price float,
quantity INT,
discount float,
Total_sales float,
Total_price float,
CONSTRAINT FK_branch FOREIGN KEY (branch_id)
REFERENCES Branch (branch_id),
CONSTRAINT FK_staff FOREIGN KEY (staff_id)
REFERENCES Staff (staff_id),
CONSTRAINT FK_time FOREIGN KEY (time_id)
REFERENCES Time (time_id),
CONSTRAINT FK_item FOREIGN KEY (item_id)
REFERENCES Item (item_id),
CONSTRAINT FK_payment FOREIGN KEY (payment_id)
REFERENCES Payment (payment_id)
);


CREATE TABLE Branch (
branch_id int NOT NULL PRIMARY KEY,
branch_name varchar (30),
address varchar (100),
city varchar (20),
contact varchar (20)
);

CREATE TABLE Time (
time_id INTEGER NOT NULL PRIMARY KEY,
day number (10),
year number (10),
month varchar (
);
CREATE TABLE Staff (
staff_id INT NOT NULL PRIMARY KEY,
staff_name varchar (50),
staff_position varchar (50),
gender varchar (20),
address varchar (100),
contact varchar (20)
);

CREATE TABLE Item (
item_id int NOT NULL PRIMARY KEY,
item_name varchar (50),
item_type varchar (50),
description varchar (100),
unit_price varchar (20)
);

CREATE TABLE Payment (
payment_id int NOT NULL PRIMARY KEY,
payment_type varchar (20)
);
