Thursday, May 25, 2017

SQL Advanced Join - Placements

 Problem
You are given three tables: Students, Friends and Packages. Students contains two columns: ID and Name. Friends contains two columns: ID and Friend_ID (ID of the ONLY best friend). Packages contains two columns: ID and Salary (offered salary in $ thousands per month).

Write a query to output the names of those students whose best friends got offered a higher salary than them. Names must be ordered by the salary amount offered to the best friends. It is guaranteed that no two students got same salary offer.
Sample Input

Sample Output
Samantha
Julia
Scarlet

Explanation
See the following table:

Now,
  • Samantha's best friend got offered a higher salary than her at 11.55
  • Julia's best friend got offered a higher salary than her at 12.12
  • Scarlet's best friend got offered a higher salary than her at 15.2
  • Ashley's best friend did NOT get offered a higher salary than her
The name output, when ordered by the salary offered to their friends, will be:
  • Samantha
  • Julia
  • Scarlet
My Answer
select s.name
    from Packages p1
    inner join Friends f on p1.ID = f.ID
    inner join Students s on f.ID = s.ID
    inner join Packages p2 on p2.ID = f.Friend_ID
    where p1.Salary < p2.Salary
order by p2.Salary

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