How GROUP BY changes query execution in SQL - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to group rows by the column 'category'.

SQL

SELECT category, COUNT(*) FROM products [1] category;

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

AWHERE

BORDER BY

CGROUP BY

DHAVING

Attempts:

3 left

💡 Hint

Common Mistakes

Using ORDER BY instead of GROUP BY

Using WHERE to filter groups

The GROUP BY clause groups rows that have the same values in specified columns. Here, it groups rows by 'category'.

2fill in blank

medium

Complete the code to filter groups having more than 5 items.

SQL

SELECT category, COUNT(*) FROM products GROUP BY category [1] COUNT(*) > 5;

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

AHAVING

BWHERE

CORDER BY

DGROUP BY

Attempts:

3 left

💡 Hint

Common Mistakes

Using WHERE instead of HAVING to filter groups

Using ORDER BY to filter groups

The HAVING clause filters groups after aggregation. It is used to filter groups based on aggregate functions like COUNT.

3fill in blank

hard

Fix the error in the query by completing the blank with the correct clause.

SQL

SELECT category, price FROM products [1] category;

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

AORDER BY

BWHERE

CGROUP BY

DHAVING

Attempts:

3 left

💡 Hint

Common Mistakes

Using GROUP BY without aggregation causing errors

Using HAVING without GROUP BY

This query selects 'category' and 'price' without aggregation. To sort rows by 'category', use ORDER BY. Using GROUP BY without aggregation causes an error.

4fill in blank

hard

Fill both blanks to group by 'department' and filter groups with average salary above 50000.

SQL

SELECT department, AVG(salary) FROM employees [1] department [2] AVG(salary) > 50000;

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

AGROUP BY

BWHERE

CHAVING

DORDER BY

Attempts:

3 left

💡 Hint

Common Mistakes

Using WHERE instead of HAVING to filter groups

Not grouping before filtering groups

First, use GROUP BY to group rows by 'department'. Then, use HAVING to filter groups where the average salary is greater than 50000.

5fill in blank

hard

Fill all three blanks to select department names in uppercase, average salary as avg_sal, and filter groups with avg_sal above 60000.

SQL

SELECT [1], AVG(salary) AS [2] FROM employees [3] department HAVING AVG(salary) > 60000;

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

AUPPER(department)

Bavg_sal

CGROUP BY

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Not aliasing the aggregate column

Using HAVING without GROUP BY

Selecting columns not in GROUP BY or aggregated

Use UPPER(department) to show department names in uppercase. Alias the average salary as avg_sal. Group rows by department using GROUP BY before filtering with HAVING.