https://github.com/tunjis/world-database-analysis_sql
https://github.com/tunjis/world-database-analysis_sql
data-analysis mysql sql
Last synced: 7 months ago
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- Host: GitHub
- URL: https://github.com/tunjis/world-database-analysis_sql
- Owner: tunjis
- Created: 2025-04-22T08:38:22.000Z (10 months ago)
- Default Branch: main
- Last Pushed: 2025-04-22T12:48:24.000Z (10 months ago)
- Last Synced: 2025-04-24T04:59:49.458Z (9 months ago)
- Topics: data-analysis, mysql, sql
- Homepage:
- Size: 86.9 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
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Metadata Files:
- Readme: README.md
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README
# 📊 World-Database-Analysis 
**MySQL**
[word db(1).sql](https://justit831-my.sharepoint.com/:u:/g/personal/justincracium_bootcamp_justit_co_uk/EYFUDcPxgehEhuULTiBi8-EBkN6T5jyUOKS7JTGi18Ei1w?e=xqeYqF)
**Objective:** To demonstrate proficiency in SQL by querying the `world` database to answer a variety of analytical questions, showcasing skills in data retrieval, filtering, aggregation, and joining techniques.
**Key Activities & Skills Demonstrated:**
* **Database Setup:** Utilised the standard `world` database schema containing information about countries, cities, and languages.
* **Data Retrieval (`SELECT`):** Extracted specific columns and all columns (`*`) from tables. Used `AS` to create meaningful aliases for columns.
* **Filtering (`WHERE`):** Applied various conditions using operators like `=`, `>`, `BETWEEN`, `LIKE` (with `%` wildcard), and `IS NOT NULL` to isolate specific data subsets.
* **Sorting (`ORDER BY`):** Arranged results in ascending (`ASC`) and descending (`DESC`) order based on column values.
* **Limiting Results (`LIMIT`):** Restricted the number of rows returned, including using offsets to fetch specific ranges.
* **Aggregation (`GROUP BY`, Aggregate Functions):** Grouped data using `GROUP BY` and performed calculations using functions like `COUNT()` and `AVG()`. Applied `ROUND()` for cleaner numerical output.
* **Joining Tables (`JOIN`):** Combined data from multiple tables (`city`, `country`) based on related columns (e.g., `CountryCode`, `Capital ID`) using `JOIN` clauses (implicitly INNER JOIN).
* **Calculations:** Performed arithmetic calculations within queries (e.g., Population Density, GNP per Capita).
* **Subqueries:** Used subqueries for complex filtering conditions (e.g., finding cities in countries with above-average GNP per capita).
---
**Schema for the 'word' database** 
---
## 💡 SQL Query Examples & Scenarios
Here are the specific SQL queries used to address the analytical tasks based on the `world` database:
1. **Count Cities in USA:** Determine the total number of cities within the United States.
```sql
SELECT COUNT(*) AS TotalUSACities
FROM city
WHERE CountryCode = 'USA';
```
2. **Country with Highest Life Expectancy:** Identify the country with the highest life expectancy.
```sql
SELECT Name, LifeExpectancy
FROM country
WHERE LifeExpectancy IS NOT NULL
ORDER BY LifeExpectancy DESC
LIMIT 1;
```
3. **Cities Containing 'New':** Compile a list of world cities whose names include 'New'.
```sql
SELECT Name, CountryCode
FROM city
WHERE Name LIKE '%New%'
ORDER BY Name;
```
4. **Top 10 Most Populous Cities:** List the first 10 cities by population globally.
```sql
SELECT Name, CountryCode, Population
FROM city
ORDER BY Population DESC
LIMIT 10;
```
5. **Cities with Population > 2 Million:** Identify cities with populations exceeding 2 million.
```sql
SELECT Name, CountryCode, Population
FROM city
WHERE Population > 2000000
ORDER BY Population DESC;
```
6. **Cities Starting with 'Be':** Compile a list of cities starting with the prefix 'Be'.
```sql
SELECT Name, CountryCode
FROM city
WHERE Name LIKE 'Be%'
ORDER BY Name;
```
7. **Mid-Sized Cities (Population 500k-1M):** Identify cities with populations between 500,000 and 1 million.
```sql
SELECT Name, CountryCode, Population
FROM city
WHERE Population BETWEEN 500000 AND 1000000
ORDER BY Population DESC;
```
8. **Cities Sorted Alphabetically:** Provide a list of all cities sorted by name (A-Z).
```sql
SELECT Name, CountryCode
FROM city
ORDER BY Name ASC;
```
9. **Most Populated City:** Identify the single most populated city in the database.
```sql
SELECT Name, CountryCode, Population
FROM city
ORDER BY Population DESC
LIMIT 1;
```
10. **City Name Frequency Analysis:** List unique city names alphabetically with their counts.
```sql
SELECT Name, COUNT(*) AS Frequency
FROM city
GROUP BY Name
ORDER BY Name ASC;
```
11. **City with Lowest Population:** Identify the city with the smallest population.
```sql
SELECT Name, CountryCode, Population
FROM city
ORDER BY Population ASC
LIMIT 1;
```
12. **Country with Largest Population:** Identify the country with the highest population.
```sql
SELECT Name, Population
FROM country
ORDER BY Population DESC
LIMIT 1;
```
13. **Capital of Spain:** Identify the capital city of Spain.
```sql
SELECT city.Name AS CapitalCity
FROM country
JOIN city ON country.Capital = city.ID
WHERE country.Code = 'ESP';
```
14. **Cities in Europe:** Compile a list of cities located on the continent of Europe.
```sql
SELECT city.Name AS CityName, country.Name AS CountryName
FROM city
JOIN country ON city.CountryCode = country.Code
WHERE country.Continent = 'Europe'
ORDER BY city.Name ASC;
```
15. **Average City Population by Country:** Calculate the average city population for each country.
```sql
SELECT
country.Name AS CountryName,
ROUND(AVG(city.Population), 0) AS AverageCityPopulation -- Calculate and round average
FROM
city
JOIN -- INNER JOIN is default
country ON city.CountryCode = country.Code
GROUP BY
country.Code, country.Name -- Group results per country
ORDER BY
country.Name ASC; -- Sort alphabetically
```
16. **Capital Cities Population Comparison:** List capital cities worldwide, ordered by population.
```sql
SELECT
city.Name AS CapitalCity,
country.Name AS CountryName,
city.Population AS CapitalPopulation
FROM
city
JOIN
country ON city.ID = country.Capital -- Link city to country using the Capital ID
ORDER BY
city.Population DESC; -- Order by the capital's population
```
17. **Countries with Low Population Density:** Identify the 25 countries with the lowest population density (people per square km).
```sql
SELECT
Name,
Population,
SurfaceArea,
ROUND((Population / SurfaceArea), 2) AS PopulationDensity_PerSqKm -- Calculate and round density
FROM
country
WHERE
SurfaceArea > 0 AND Population > 0 -- Exclude uninhabited areas or those with zero area
ORDER BY
PopulationDensity_PerSqKm ASC -- Order by density, lowest first
LIMIT 25; -- Show the 25 least dense
```
18. **Cities with High GNP per Capita (Country Level):** Identify cities located in countries with an above-average Gross National Product (GNP) per capita.
```sql
SELECT
city.Name AS CityName,
country.Name AS CountryName,
ROUND((country.GNP / country.Population), 2) AS CountryGNP_PerCapita -- Show country's figure
FROM
city
JOIN
country ON city.CountryCode = country.Code
WHERE
country.Population > 0 AND country.GNP > 0 -- Ensure valid data for calculation
AND (country.GNP / country.Population) > (
-- Subquery calculates the overall average country GNP per capita
SELECT AVG(GNP / Population)
FROM country
WHERE Population > 0 AND GNP > 0 AND GNP IS NOT NULL
)
ORDER BY
CountryGNP_PerCapita DESC, -- Show cities in highest GNP-per-capita countries first
country.Name ASC,
city.Name ASC;
```
19. **Cities Ranked 31-40 by Population:** List cities ranked 31st to 40th by population.
```sql
SELECT Name, CountryCode, Population
FROM city
ORDER BY Population DESC
LIMIT 30, 10; -- Skip 30 rows, take the next 10
```
---
### Summary of Key SQL Skills Demonstrated:
* **Data Querying:** `SELECT`, `FROM`, `WHERE`.
* **Filtering:** Comparison operators (`=`, `>`, `BETWEEN`), `LIKE`, `IS NOT NULL`.
* **Sorting & Limiting:** `ORDER BY` (`ASC`, `DESC`), `LIMIT` (including offset).
* **Aggregation:** `GROUP BY`, `COUNT()`, `AVG()`.
* **Joining:** `JOIN ... ON` (primarily INNER joins demonstrated).
* **Data Manipulation:** Aliasing (`AS`), basic arithmetic, `ROUND()`.
* **Subqueries:** Used for filtering based on aggregated results.
---
### 🧑💻 Created by [tunjis](https://github.com/tunjis)
* 🌍 Based in **London**
* 🖥️ See my portfolio at [Data’s the new oil. I’m the refinery.](https://github.com/tunjis?tab=repositories)
* 📫 Contact me via my [LinkedIn profile](https://linkedin.com/in/justincraciun/)
* 🧠 Learning Data Science
* 🤝 Open to collaborating on interesting projects
* ⚡ AI enthusiast
---
### 🛠️ Technical Skills
**Python**
**Microsoft Excel**
**MySQL**
**Tableau**
**Power BI**
**Microsoft Azure**
**Google Cloud**
**Google Colab**
---
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