Added readme and some questions/solutions

Author: peteryates

README.md

@@ -30,4 +30,70 @@ This repository contains a sample PostgreSQL database aimed at helping people ne
 
 ## Schema
 
+```mermaid
+erDiagram
+
+    athlete {
+        id integer
+        name varchar
+        sex sex
+        height integer
+        weight integer
+    }
+
+    sport {
+        id integer
+        name varchar
+    }
+
+    country {
+        code char
+        name varchar
+        alternative_name varchar
+    }
+
+    games {
+        code char
+        name varchar
+        year integer
+        season season "Summer or Winter"
+        city varchar
+    }
+
+    event {
+        id integer
+        sport_id integer
+        name varchar
+        sex sex
+    }
+
+    appearance {
+        athlete_id integer
+        country_code char
+        games_code char
+        event_id integer
+        age integer
+        medal medal
+    }
+
+
+    athlete ||--|{ appearance : competes
+    country ||--|{ appearance : "represents"
+    games ||--|{ appearance : "is made at"
+    sport ||--|{ event : "belongs to"
+    event ||--|{ appearance : "in"
+```
+
 ## Questions
+
+1. How many gymnastics events are there?
+2. When and where were the first Winter Olympic Games?
+3. Which athlete taller than 2m has the last name alphabetically?
+4. Who is the youngest ever competitor at any games?
+5. Which five events have the longest names?
+6. Which sports did France win medals at in teh 1952 summer games?
+7. Which country won the most biathlon medals between 1990 and 2010?
+8. Which sports were included before 1920 but not after?
+9. Which ten countries have the most gold medals in table tennis?
+10. How many games did Linford Christie compete at?
+11. How many athletes have competed at both the summer and winter Olympic games?

ddl/appearance.sql

@@ -1,6 +1,6 @@
 drop table if exists appearance;
 
-create type medal as enum ('Gold', 'Silver', 'Bronze');
+create type medal as enum ('Bronze', 'Silver', 'Gold');
 
 create table appearance (
 	athlete_id integer not null references athlete(id),

questions/01-how-many-gymnastics-events-are-there.sql

@@ -0,0 +1,9 @@
+-- how many gymnastic events are there?
+
+select
+	count(*)
+from sport s
+	inner join event e
+		on s.id = e.sport_id
+where
+	s.name = 'Gymnastics';

questions/02-when-and-where-was-the-first-winter-olympics.sql

@@ -0,0 +1,14 @@
+-- when and where were the first Winter Olympic Games held?
+
+select
+	year,
+	city
+from
+	games
+where
+	season = 'Winter'
+order by
+	year asc
+limit
+	1
+;

questions/03-which-athlete-taller-than-2m-has-the-final-name-alphabetically.sql

@@ -0,0 +1,12 @@
+-- which athlete taller than 2m has the last name when sorted alphabetically?
+
+select
+	name
+from
+	athlete
+where
+	height >= 200
+order by
+	name desc
+limit
+	1;

questions/04-who-is-the-youngest-ever-competitor.sql

@@ -0,0 +1,17 @@
+-- who is the youngest ever competitor?
+
+select
+	ath.name,
+	c.name as country
+from
+	appearance ap
+inner join
+	athlete ath
+		on ap.athlete_id = ath.id
+inner join
+	country c
+		on ap.country_code = c.code
+order by
+	age asc
+limit
+	1;

questions/05-which-five-events-have-the-longest-names.sql

@@ -0,0 +1,11 @@
+-- which five events have the longest names?
+
+select
+	name,
+	length(name) size
+from
+	event
+order by
+	size desc
+limit
+	5;

questions/06-which-sports-did-france-win-medals-in-at-the-1952-summer-games.sql

@@ -0,0 +1,21 @@
+-- which sports did France win medals at in the 1952 summer games?
+
+select
+	distinct(s.name)
+from
+	appearance a
+inner join
+	event e
+		on a.event_id = e.id
+inner join
+	sport s
+		on e.sport_id = s.id
+inner join
+	games g
+		on a.games_code = g.code
+where
+	g.year = 1952
+and
+	g.season = 'Summer'
+and
+	a.country_code = 'FRA';

questions/07-which-country-won-most-biathlon-medals-from-1990-to-2010.sql

@@ -0,0 +1,31 @@
+-- which country won most biathlon medals between 1990 and 2010
+
+select
+	c.name,
+	count(*) quantity
+from
+	appearance a
+inner join
+	event e
+		on a.event_id = e.id
+inner join
+	sport s
+		on e.sport_id = s.id
+inner join
+	country c
+		on a.country_code = c.code
+inner join
+	games g
+		on a.games_code = g.code
+where
+	s.name = 'Biathlon'
+and
+	a.medal is not null
+and
+	g.year between 1990 and 2010
+group by
+	c.name
+order by
+	quantity desc 
+limit
+	1

questions/08-which-sports-were-no-longer-included-after-1920.sql

@@ -0,0 +1,25 @@
+-- which sports were played before 1920 but not after?
+
+with sports_played_after_1920 as (
+	select
+		distinct(s.id)
+	from
+		appearance a
+	inner join
+		event e
+			on a.event_id = e.id
+	inner join
+		sport s
+			on e.sport_id = s.id
+	inner join
+		games g
+			on a.games_code = g.code
+	where
+		g.year >= 1920
+)
+select
+	name
+from
+	sport
+where
+	id not in (select id from sports_played_after_1920);