Why aggregation is needed in SQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the total sales from the sales table.

SQL

SELECT [1](amount) FROM sales;

Drag options to blanks, or click blank then click option'

AMIN

BCOUNT

CMAX

DSUM

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT counts rows, not sums values.

Using MAX or MIN returns only the highest or lowest value.

The SUM function adds all the values in the amount column to give the total sales.

2fill in blank

medium

Complete the code to find how many orders are in the orders table.

SQL

SELECT [1](*) FROM orders;

Drag options to blanks, or click blank then click option'

ASUM

BAVG

CCOUNT

DMAX

Attempts:

3 left

💡 Hint

Common Mistakes

Using SUM tries to add values but * is not a column.

Using AVG or MAX does not count rows.

The COUNT function counts the number of rows, which tells how many orders there are.

3fill in blank

hard

Fix the error in the code to find the average price from the products table.

SQL

SELECT [1](price) FROM products;

Drag options to blanks, or click blank then click option'

AAVG

BCOUNT

CSUM

DMIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using SUM adds all prices instead of averaging.

Using COUNT counts rows, not values.

Using MIN finds the smallest price.

The AVG function calculates the average value of the price column.

4fill in blank

hard

Fill both blanks to find the highest and lowest scores from the scores table.

SQL

SELECT [1](score), [2](score) FROM scores;

Drag options to blanks, or click blank then click option'

AMAX

BMIN

CSUM

DCOUNT

Attempts:

3 left

💡 Hint

Common Mistakes

Using SUM or COUNT does not find highest or lowest values.

Swapping MAX and MIN changes the meaning.

MAX finds the highest score, and MIN finds the lowest score.

5fill in blank

hard

Fill all three blanks to create a query that shows each department, the number of employees, and the average salary from the employees table.

SQL

SELECT [1], [2](employee_id), [3](salary) FROM employees GROUP BY [1];

Drag options to blanks, or click blank then click option'

Adepartment

BCOUNT

CAVG

DSUM

Attempts:

3 left

💡 Hint

Common Mistakes

Using SUM instead of AVG for salary.

Not grouping by department.

Counting salary instead of employee_id.

This query groups employees by department, counts employees with COUNT, and calculates average salary with AVG.