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Enhance SQL exercises with population calculations #104

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35 changes: 26 additions & 9 deletions SQL Deep Dive/Window Functions/exercises.sql
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,10 @@
* Database: World
* Table: Country
*/

SELECT *
FROM country;

SELECT DISTINCT continent, SUM(population)
OVER w1 AS "Continent Population"
FROM country
WINDOW w1 AS (PARTITION BY continent);
/*
* To the previous query add on the ability to calculate the percentage of the world population
* What that means is that you will divide the population of that continent by the total population and multiply by 100 to get a percentage.
Expand All @@ -16,10 +16,18 @@ FROM country;
* Database: World
* Table: Country
*/

SELECT *
FROM country;

SELECT
DISTINCT continent,
SUM(population) OVER w1 as"continent population",
CONCAT(
ROUND(
(
SUM(population::float4) OVER w1 /
SUM(population::float4) OVER()
) * 100
),'%' ) as "% of population"
FROM country
WINDOW w1 AS( PARTITION BY continent );

/*
* Count the number of towns per region
Expand All @@ -28,5 +36,14 @@ FROM country;
* Table: Regions (Join + Window function)
*/

SELECT *
SELECT DISTINCT r.id,
r."name",
COUNT(t.id) OVER(
PARTITION BY r.id
ORDER BY r."name"
) AS "No of towns"
FROM regions as r
JOIN departments as d ON r.code = d.region
JOIN towns as t ON d.code = t.department
ORDER BY r.id;
FROM regions AS r;