HackerRank SQL練習題答案大全

太弱智的就不寫了

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• Weather Observation Station 5

select city,length(city) from station order by length(city),city limit 1;
select city,length(city) from station order by length(city) desc,city limit 1;

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• Weather Observation Station 8

select city from station where city REGEXP '^[AEIOU].*[aeiou]$'; 

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• Higher Than 75 Marks

select name from students where marks > 75 order by right(name,3),id asc;

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• Type of Triangle

select
case when(a+b>c and a+c>b and c+b>a) then (
case when(a=b and b=c) then 'Equilateral'
when(a=b or b=c or a=c) then 'Isosceles'
else 'Scalene' end
)
else 'Not A Triangle' end
from triangles;

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• The Blunder

select ceil(AVG(salary) - AVG(replace(salary,'0',''))) from employees;

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• Top Earners

select max(salary*months),count(employee_id) from employee where salary*months = (select max(salary*months) from employee);

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• Weather Observation Station 18

set @a =(select min(lat_n) from station);
set @b = (select min(long_w) from station);
set @c = (select max(lat_n) from station);
set @d = (select max(long_w) from station);
select round(@c+@d-@a-@b,4);

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• Draw The Triangle 1

set @i = 21;
select repeat('* ',@i:=@i-1) from information_schema.tables limit 20;

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• Binary Tree Nodes

/*
Enter your query here.
*/
select B2.N,
case when ((select count(*) from BST B1 where B1.P = B2.N)=0) then 'Leaf'
when (isnull(B2.P) = 1) then 'Root'
else 'Inner' end
from BST B2 order by B2.N;

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• Placements

/*
Enter your query here.
*/
select
T.name
from (
    select 
    S.Id Id,
    S.name name,
    P.Salary Salary,
    F.Friend_Id FId,
    (select Packages.Salary from Packages where Packages.Id=FId) FSalary
    FROM Students S, Friends F, Packages P
    where F.Id=S.Id
    and P.Id=S.Id
) T
where FSalary>Salary
order by FSalary;