arcade databases task using case/when

Author: jorzel

arcade/databases/orderOfSuccession.mysql

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+/*
+The kingdom has been given terrible news: the King has passed away. While the nation is mourning, the noblemen need to decide who will take the throne next.
+
+The late King had many children, and now it is necessary to determine their order of succession according to their seniority.
+
+The list of the King's children is represented as a table Successors with the following attributes:
+
+name: the child's name;
+birthday: the date of their birthday (it is guaranteed that birthday dates are unique);
+gender: their gender (a character equal to 'M' or 'F').
+The resulting table should contain the names of the King's heirs in order of their succession to the throne as determined by their age, and preceded by their potential future titles (i.e. "King name" or "Queen name").
+
+Example
+
+For the following table Successors
+
+name	birthday	gender
+Amelia	1711-06-10	F
+Anne	1709-11-02	F
+Caroline	1713-06-10	F
+Frederick	1707-02-01	M
+Loisa	1724-12-18	F
+Mary	1723-03-05	F
+William	1721-04-26	M
+The output should be
+
+name
+King Frederick
+Queen Anne
+Queen Amelia
+Queen Caroline
+King William
+Queen Mary
+Queen Loisa
+*/
+
+CREATE PROCEDURE orderOfSuccession()
+BEGIN
+	select
+        (case when gender = 'M' then CONCAT('King ', name) else CONCAT('Queen ', name) end) as name
+    from Successors order by birthday;
+END

arcade/databases/orderingEmails.mysql

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+/*
+You've started to receive a lot of emails every day, and you decide to sort them in order to make it quicker to navigate through them.
+
+Information about your emails is stored in a table emails, which has the following structure:
+
+id: the unique email id;
+email_title: the title of the email;
+size: the size of the email's body in bytes.
+You decide to sort all the emails by their body sizes in descending order, because you think that the bigger an email is the more important it is. However, you don't like having the sizes written in bytes because they are usually too large and don't make much sense. You want them to be written in kilobytes (1 Kb = 210 bytes) and megabytes (1 Mb = 220 bytes) instead, rounded down if necessary. For example, 21432432 bytes is equal to 20 megabytes and 460912 bytes, so the result should be rounded down to 20 Mb.
+
+Given the table emails, build a table as follows: The resulting table should have the columns id, email_title, and short_size, and should be sorted in descending order by the initial sizes of the emails. It is guaranteed that all the emails are of unique sizes, so there will not be any ties.
+
+Example
+
+For the following table emails
+
+id	email_title	size
+1	You won 1M dollars!	21432432
+2	You are fired	312342
+3	Black Friday is coming	323
+4	Spam email	23532
+5	Your requested backup	234234324
+the output should be
+
+id	email_title	short_size
+5	Your requested backup	223 Mb
+1	You won 1M dollars!	20 Mb
+2	You are fired	305 Kb
+4	Spam email	22 Kb
+3	Black Friday is coming	0 Kb
+*/
+
+CREATE PROCEDURE orderingEmails()
+BEGIN
+	select
+        id,
+        email_title,
+        case
+        when size < 1024 then '0 Kb'
+        when size >= 1024 and size < 1024 * 1024 then concat(floor(size / 1024), ' Kb')
+        when size >= 1024 * 1024 then concat(floor(size / (1024 * 1024)), ' Mb')
+        END as short_size
+     from emails order by size desc;
+END

arcade/databases/placesOfInterest.mysql

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+/*
+You are trying to decide where you want to go on your vacation, so your travel agency has provided you with a database of possible destinations.
+
+This database contains the table countryActivities, which has the following structure:
+
+id: the unique id of the record;
+country: the country name;
+region: the region of this country;
+leisure_activity_type: the type of activity provided in the region. This can only be equal to one of the following values: Adventure park, Golf, Kart racing, River cruise;
+number_of_places: the number of resorts in the region at which you can do this activity.
+You want to see how many resorts in each country provide the activities you are interested in before you decide where to go on your vacation, but it's hard to do this using only the table provided by your travel agency. To make things easier, you have decided to create a new table with a better structure.
+
+Given the countryActivities table, compose the resulting table with five columns: country, adventure_park, golf, river_cruise and kart_racing. The first column should contain the country name, while the second, third, fourth, and fifth columns should contain the number of resorts in the country that offer Adventure park, Golf, River cruise, and Kart racing, respectively. The table should be sorted by the country names in ascending order.
+
+Example
+
+For the following table countryActivities
+
+id	country	region	leisure_activity_type	number_of_places
+1	France	Normandy	River cruise	2
+2	Germany	Bavaria	Golf	5
+3	Germany	Berlin	Adventure park	2
+4	France	Ile-de-France	River cruise	1
+5	Sweden	Stockholm	River cruise	3
+6	France	Normandy	Kart racing	4
+the output should be
+
+country	adventure_park	golf	river_cruise	kart_racing
+France	0	0	3	4
+Germany	2	5	0	0
+Sweden	0	0	3	0
+*/
+
+CREATE PROCEDURE placesOfInterest()
+BEGIN
+	select
+    country,
+    sum(case when leisure_activity_type = 'Adventure Park' then number_of_places else 0 end) as adventure_park,
+    sum(case when leisure_activity_type = 'Golf' then number_of_places else 0 end) as golf,
+    sum(case when leisure_activity_type = 'River cruise' then number_of_places else 0 end) as river_cruises,
+    sum(case when leisure_activity_type = 'Kart racing' then number_of_places else 0 end) as kart_racing
+    from countryActivities group by country order by country;
+END

arcade/databases/soccerGameSeries.mysql

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+/*
+You have a table scores that contains information about a series of soccer games. Your goal is to determine the winner of the series. A team is declared the winner if it won more games than the other team. If both teams had the same number of wins, then the winner is determined by the better goal difference (the difference between the goals that a team scores and the goals that the opposing team scores on them over all the games). If the goal differences are equal, the winner is the team that scored more goals during away games (i.e. games when it was not the host team). The result is the index of the winning team. If the above criteria are not sufficient for determining the winner, return 0.
+
+The scores table contains the following columns:
+
+match_id - the unique ID of the match;
+first_team_score - the score of the 1st team in the current match;
+second_team_score - the score of the 2nd team in the current match;
+match_host - the team that is the host of the match (can be 1 or 2).
+Your task is to write a select statement which returns a single column winner, which can contain 1, 2, or 0.
+
+Example
+
+For given table scores
+
+match_id	first_team_score	second_team_score	match_host
+1	3	2	1
+2	2	1	2
+3	1	2	1
+4	2	1	2
+the output should be
+
+winner
+1
+The first team won 3 games out of 4, so it's the winner of the series.
+*/
+
+
+CREATE PROCEDURE soccerGameSeries()
+BEGIN
+    select
+    (case
+        when y.first_team_wins > y.second_team_wins then 1
+        when y.first_team_wins < y.second_team_wins then 2
+        else (
+            case
+                when y.first_team_goals > y.second_team_goals then 1
+                when y.first_team_goals < y.second_team_goals then 2
+                else (
+                case
+                    when y.first_team_away_goals > y.second_team_away_goals then 1
+                    when y.first_team_away_goals < y.second_team_away_goals then 2
+                    else 0
+                end
+                )
+            end
+        )
+    end
+    ) as winner
+    from (
+        select
+        sum(case when x.winner = 1 then 1 else 0 end) as first_team_wins,
+        sum(case when x.winner = 2 then 1 else 0 end) as second_team_wins,
+        sum(x.first_team_away_goals) as first_team_away_goals,
+        sum(x.second_team_away_goals) as second_team_away_goals,
+        sum(x.first_team_goals) as first_team_goals,
+        sum(x.second_team_goals) as second_team_goals
+        from (
+            select
+            (case
+                when first_team_score > second_team_score then 1
+                when first_team_score < second_team_score then 2
+                else 0
+            end) as winner,
+            (case when match_host = 2 then first_team_score else 0 end) as first_team_away_goals,
+            (case when match_host = 1 then second_team_score else 0 end) as second_team_away_goals,
+            first_team_score as first_team_goals,
+            second_team_score as second_team_goals
+            from scores
+        ) as x
+    ) as y;
+END