#470 SQL Queries for Countries, Population, and GDP

The following tables are given:

CREATE TABLE country (
    id          SERIAL
    name        VARCHAR(100)
    continent   VARCHAR(50)
    population  INT
);

CREATE TABLE gdp (
    id
    country_id  INT
    year        INT
    value       INT
);

Required:

1. Return continents and the total population of each;
2. Return continents and the total population of each where the population exceeds one billion;
3. Return the country name and GDP per capita;
4. Explain errors involving NULL and 0;
5. There are 200 rows in the country table and 180 in gdp. How many rows will the query return? Explain using set theory;
6. Return the continent, country name, and population. Show only the largest country by population on each continent;
7. The same as item 6, but return the top 3 countries.