Why grouping is needed in SQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select the total sales for each product.

SQL

SELECT product_id, SUM(sales) FROM sales_data GROUP BY [1];

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

Asales

Bproduct_id

Ctotal

Ddate

Attempts:

3 left

💡 Hint

Common Mistakes

Grouping by sales instead of product_id.

Not using GROUP BY at all.

Grouping by product_id allows us to calculate the total sales per product.

2fill in blank

medium

Complete the code to find the average score for each student.

SQL

SELECT student_name, AVG(score) FROM exam_results GROUP BY [1];

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Astudent_name

Bclass

Cscore

Dexam_date

Attempts:

3 left

💡 Hint

Common Mistakes

Grouping by score instead of student_name.

Forgetting to use GROUP BY.

Grouping by student_name lets us calculate the average score per student.

3fill in blank

hard

Fix the error in the query to get the count of orders per customer.

SQL

SELECT customer_id, COUNT(order_id) FROM orders [1] customer_id;

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AORDER BY

BWHERE

CHAVING

DGROUP BY

Attempts:

3 left

💡 Hint

Common Mistakes

Using ORDER BY instead of GROUP BY.

Using WHERE clause incorrectly.

The GROUP BY clause groups rows by customer_id so COUNT counts orders per customer.

4fill in blank

hard

Fill both blanks to get the total sales and average price per category.

SQL

SELECT category, [1](sales), [2](price) FROM products GROUP BY category;

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ASUM

BAVG

CCOUNT

DMAX

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT instead of SUM or AVG.

Mixing up SUM and AVG functions.

Use SUM to add sales and AVG to find average price per category.

5fill in blank

hard

Fill all three blanks to get the number of employees, average salary, and maximum age per department.

SQL

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

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

ACOUNT

BAVG

CMAX

DMIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using MIN instead of MAX for age.

Using SUM instead of COUNT for employee count.

Use COUNT to count employees, AVG for average salary, and MAX for maximum age per department.