CREATE TABLE country(
name VARCHAR(40) NOT NULL PRIMARY KEY,
capital VARCHAR(40),
areaOfCapital VARCHAR(40),
currency VARCHAR(20),
FOREIGN KEY (capital) REFERENCES cityPopulation (city),
FOREIGN KEY (currency) REFERENCES currencyValue (currency)
);

CREATE TABLE country-cities(
name VARCHAR(40) NOT NULL PRIMARY KEY,
capital VARCHAR(40),
areaOfCapital VARCHAR(40),
central VARCHAR(20),
FOREIGN KEY (capital) REFERENCES cityPopulation (city),
FOREIGN KEY (central) REFERENCES cityPopulation (city)
);

CREATE TABLE currencyValue(
currency VARCHAR(30) NOT NULL,
year VARCHAR(30) NOT NULL,
valueInUSD VARCHAR(30),
PRIMARY KEY (currency,year)
);

CREATE TABLE cityPopulation(
city VARCHAR(30) NOT NULL,
date VARCHAR(30) NOT NULL,
population VARCHAR(30),
PRIMARY KEY (city,date)
);

CREATE TABLE export(
supplier VARCHAR(40) NOT NULL,
consumer VARCHAR(40) NOT NULL,
amount VARCHAR(40),
PRIMARY KEY (supplier,consumer),
FOREIGN KEY (supplier) REFERENCES country (name),
FOREIGN KEY (consumer) REFERENCES country (name)
);

CREATE TABLE company(
coName VARCHAR(40) NOT NULL PRIMARY KEY,
country VARCHAR(40),
revenues VARCHAR(40),
FOREIGN KEY (country) REFERENCES country (name)
);

CREATE TABLE european(
country VARCHAR(40) NOT NULL PRIMARY KEY,
gnp VARCHAR(40),
FOREIGN KEY (country) REFERENCES country (name)
);