Medium set started- 4 Questions attempted

Author: mrinal1704

Medium/Consecutive Numbers.sql

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+-- Question 52
+-- Write a SQL query to find all numbers that appear at least three times consecutively.
+
+-- +----+-----+
+-- | Id | Num |
+-- +----+-----+
+-- | 1  |  1  |
+-- | 2  |  1  |
+-- | 3  |  1  |
+-- | 4  |  2  |
+-- | 5  |  1  |
+-- | 6  |  2  |
+-- | 7  |  2  |
+-- +----+-----+
+-- For example, given the above Logs table, 1 is the only number that appears consecutively for at least three times.
+
+-- +-----------------+
+-- | ConsecutiveNums |
+-- +-----------------+
+-- | 1               |
+-- +-----------------+
+
+-- Solution
+select distinct a.num as ConsecutiveNums
+from(
+select *,
+lag(num) over() as prev,
+lead(num) over() as next
+from logs) a
+where a.num = a.prev and a.num=a.next

Medium/Nth Highest salary.sql

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+-- Question 50
+-- Write a SQL query to get the nth highest salary from the Employee table.
+
+-- +----+--------+
+-- | Id | Salary |
+-- +----+--------+
+-- | 1  | 100    |
+-- | 2  | 200    |
+-- | 3  | 300    |
+-- +----+--------+
+-- For example, given the above Employee table, the nth highest salary where n = 2 is 200. If there is no nth highest salary, then the query should return null.
+
+-- +------------------------+
+-- | getNthHighestSalary(2) |
+-- +------------------------+
+-- | 200                    |
+-- +------------------------+
+
+-- Solution 
+CREATE FUNCTION getNthHighestSalary(N INT) RETURNS INT
+BEGIN
+  RETURN (
+      # Write your MySQL query statement below.
+      select distinct a.salary
+      from
+      (select salary, 
+      dense_rank() over(order by salary desc) as rk
+      from Employee) a
+      where a.rk = N
+  );
+END

Medium/Rank scores.sql

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+-- Question 51
+-- Write a SQL query to rank scores.
+-- If there is a tie between two scores, both should have the same ranking. 
+-- Note that after a tie, the next ranking number should be the next consecutive integer value. 
+-- In other words, there should be no "holes" between ranks.
+
+-- +----+-------+
+-- | Id | Score |
+-- +----+-------+
+-- | 1  | 3.50  |
+-- | 2  | 3.65  |
+-- | 3  | 4.00  |
+-- | 4  | 3.85  |
+-- | 5  | 4.00  |
+-- | 6  | 3.65  |
+-- +----+-------+
+-- For example, given the above Scores table, your query should generate the following report (order by highest score):
+
+-- +-------+---------+
+-- | score | Rank    |
+-- +-------+---------+
+-- | 4.00  | 1       |
+-- | 4.00  | 1       |
+-- | 3.85  | 2       |
+-- | 3.65  | 3       |
+-- | 3.65  | 3       |
+-- | 3.50  | 4       |
+-- +-------+---------+
+-- Important Note: For MySQL solutions, to escape reserved words used as column names, 
+-- you can use an apostrophe before and after the keyword. For example `Rank`.
+
+-- Solution
+select Score,
+dense_rank() over(order by score desc) as "Rank"
+from scores

Medium/Team scores in football match.sql

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+-- Question 53
+-- Table: Teams
+
+-- +---------------+----------+
+-- | Column Name   | Type     |
+-- +---------------+----------+
+-- | team_id       | int      |
+-- | team_name     | varchar  |
+-- +---------------+----------+
+-- team_id is the primary key of this table.
+-- Each row of this table represents a single football team.
+-- Table: Matches
+
+-- +---------------+---------+
+-- | Column Name   | Type    |
+-- +---------------+---------+
+-- | match_id      | int     |
+-- | host_team     | int     |
+-- | guest_team    | int     | 
+-- | host_goals    | int     |
+-- | guest_goals   | int     |
+-- +---------------+---------+
+-- match_id is the primary key of this table.
+-- Each row is a record of a finished match between two different teams. 
+-- Teams host_team and guest_team are represented by their IDs in the teams table (team_id) and they scored host_goals and guest_goals goals respectively.
+ 
+
+-- You would like to compute the scores of all teams after all matches. Points are awarded as follows:
+-- A team receives three points if they win a match (Score strictly more goals than the opponent team).
+-- A team receives one point if they draw a match (Same number of goals as the opponent team).
+-- A team receives no points if they lose a match (Score less goals than the opponent team).
+-- Write an SQL query that selects the team_id, team_name and num_points of each team in the tournament after all described matches. Result table should be ordered by num_points (decreasing order). In case of a tie, order the records by team_id (increasing order).
+
+-- The query result format is in the following example:
+
+-- Teams table:
+-- +-----------+--------------+
+-- | team_id   | team_name    |
+-- +-----------+--------------+
+-- | 10        | Leetcode FC  |
+-- | 20        | NewYork FC   |
+-- | 30        | Atlanta FC   |
+-- | 40        | Chicago FC   |
+-- | 50        | Toronto FC   |
+-- +-----------+--------------+
+
+-- Matches table:
+-- +------------+--------------+---------------+-------------+--------------+
+-- | match_id   | host_team    | guest_team    | host_goals  | guest_goals  |
+-- +------------+--------------+---------------+-------------+--------------+
+-- | 1          | 10           | 20            | 3           | 0            |
+-- | 2          | 30           | 10            | 2           | 2            |
+-- | 3          | 10           | 50            | 5           | 1            |
+-- | 4          | 20           | 30            | 1           | 0            |
+-- | 5          | 50           | 30            | 1           | 0            |
+-- +------------+--------------+---------------+-------------+--------------+
+
+-- Result table:
+-- +------------+--------------+---------------+
+-- | team_id    | team_name    | num_points    |
+-- +------------+--------------+---------------+
+-- | 10         | Leetcode FC  | 7             |
+-- | 20         | NewYork FC   | 3             |
+-- | 50         | Toronto FC   | 3             |
+-- | 30         | Atlanta FC   | 1             |
+-- | 40         | Chicago FC   | 0             |
+-- +------------+--------------+---------------+
+
+-- Solution
+with t1 as(
+Select c.host_id, c.host_name, c.host_points
+from(
+select a.match_id, a.team_id as host_id, a.team_name as host_name, b.team_id as guest_id, b.team_name as guest_name, a.host_goals, a.guest_goals,
+case
+when a.host_goals > a.guest_goals then 3
+when a.host_goals = a.guest_goals then 1
+else 0
+end as host_points,
+case
+when a.host_goals < a.guest_goals then 3
+when a.host_goals = a.guest_goals then 1
+else 0
+end as guest_points
+from(
+select *
+from matches m
+join teams t
+on t.team_id = m.host_team) a
+join
+(select *
+from matches m
+join teams t
+on t.team_id = m.guest_team) b
+on a.match_id = b.match_id) c
+union all
+Select d.guest_id, d.guest_name, d.guest_points
+from(
+select a.match_id, a.team_id as host_id, a.team_name as host_name, b.team_id as guest_id, b.team_name as guest_name, a.host_goals, a.guest_goals,
+case
+when a.host_goals > a.guest_goals then 3
+when a.host_goals = a.guest_goals then 1
+else 0
+end as host_points,
+case
+when a.host_goals < a.guest_goals then 3
+when a.host_goals = a.guest_goals then 1
+else 0
+end as guest_points
+from(
+select *
+from matches m
+join teams t
+on t.team_id = m.host_team) a
+join
+(select *
+from matches m
+join teams t
+on t.team_id = m.guest_team) b
+on a.match_id = b.match_id) d)
+
+Select team_id, team_name, coalesce(total,0) as num_points
+from teams t2
+left join(
+select host_id, host_name, sum(host_points) as total
+from t1
+group by host_id, host_name) e
+on t2.team_id = e.host_id
+order by num_points desc, team_id