# SUM and COUNT Quiz

[Link](https://sqlzoo.net/wiki/SUM_and_COUNT_Quiz)

1. Select the statement that shows the sum of population of all countries in 'Europe'<br>

   ```sql
   SELECT SUM(population) FROM bbc WHERE region = 'Europe'
   ```

2. Select the statement that shows the number of countries with population smaller than 150000<br>

   ```sql
    SELECT COUNT(name) FROM bbc WHERE population < 150000
   ```

3. Select the list of core SQL aggregate functions\
   **AVG(), COUNT(), MAX(), MIN(), SUM()**

4. Select the result that would be obtained from the following code:<br>

   ```sql
    SELECT region, SUM(area)
      FROM bbc 
     WHERE SUM(area) > 15000000 
     GROUP BY region
   ```

   \
   **No result due to invalid use of the WHERE function**<br>

5. Select the statement that shows the average population of 'Poland', 'Germany' and 'Denmark'

   ```sql
    SELECT AVG(population) FROM bbc 
    WHERE name IN ('Poland', 'Germany', 'Denmark')
   ```

6. Select the statement that shows the medium population density of each region<br>

   ```sql
    SELECT region, SUM(population)/SUM(area) AS density 
    FROM bbc 
    GROUP BY region
   ```

7. Select the statement that shows the name and population density of the country with the largest population<br>

   ```sql
    SELECT name, population/area AS density 
    FROM bbc 
    WHERE population = (SELECT MAX(population) FROM bbc)
   ```

8. Pick the result that would be obtained from the following code: <br>

   ```sql
    SELECT region, SUM(area) 
      FROM bbc 
     GROUP BY region 
     HAVING SUM(area)<= 20000000
   ```

| Americas      | 732240   |
| ------------- | -------- |
| Middle East   | 13403102 |
| South America | 17740392 |
| South Asia    | 9437710  |


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