Составление запросов - MySQL

select * from country where Population = (SELECT max(Population) FROM country);

select * from country where Population = (SELECT min(Population) FROM country);

select * from country where SurfaceArea = (SELECT max(SurfaceArea) FROM country);

select * from country where SurfaceArea = (SELECT min(SurfaceArea) FROM country);

 SELECT continent, sum(surfacearea)/count(*) FROM country group by continent;

SELECT 
t5.Continent,
t5.Region,
sum(t5.Countries),
sum(t5.LifeDuration),
sum(t5.Population),
sum(t5.Cities),
sum(t5.Languages)
from
(
 
select
t3.Code
t3.Continent,
t3.Region,
t3.Countries,
t3.LifeDuration,
t3.Population,
t3.Cities,
t4.Languages
from
(
select
t1.Code,
t1.Continent,
t1.Region,
t1.Countries,
t1.LifeDuration,
t1.Population,
t2.Cities
from
( 
select
Code,
Continent,
Region,
count(Name) as Countries,
ROUND(AVG(LifeExpectancy), 2) as LifeDuration, 
SUM(Population) as Population
from country
group by Code,Continent,Region
) t1 left join 
(
select
CountryCode,
count(Name) as Cities
from city
group by CountryCode 
) t2 on t2.CountryCode = t1.Code
) t3 left join 
(
select 
CountryCode,
count(Language) as Languages
from countrylanguage
group by CountryCode
) t4 on t4.CountryCode = t3.Code
) t5
group by t5.Continent,t5.Region;