LeetCode | SQL | 5题

175. Combine Two Tables

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Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people:

FirstName, LastName, City, State

select a.FirstName, a.LastName, b.City, b.State
from Person a
left join Address b
on a.PersonId = b.PersonId

176. Second Highest Salary

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select 
    (select distinct Salary 
    from Employee
    order by Salary DESC
    limit 1,1) as SecondHighestSalary;

177. Nth Highest Salary

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CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
BEGIN
  set N = N-1;    # 先令N=N-1,limit那里不能做运算
  RETURN (
      select distinct Salary 
       from Employee
       order by Salary desc
       limit N,1
  );
END

178. Rank Scores

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select Score,
       (select count(*) from (select distinct Score s from Scores) tmp 
       where s >= Score) as Rank
from Scores
order by Score desc

180. Consecutive Numbers

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select distinct l1.Num as ConsecutiveNums
from 
    Logs l1,
    Logs l2,
    Logs l3
where
    l1.id = l2.id - 1
    and l2.id = l3.id - 1
    and l1.Num = l2.Num
    and l2.Num = l3.Num
;