Why query patterns matter in SQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all columns from the employees table.

SQL

SELECT [1] FROM employees;

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

AALL

B*

Ceverything

Dcolumns

Attempts:

3 left

💡 Hint

Common Mistakes

Using words like ALL or columns instead of * causes errors.

Using * selects all columns from the table.

2fill in blank

medium

Complete the code to filter employees with salary greater than 50000.

SQL

SELECT * FROM employees WHERE salary [1] 50000;

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

A>

B=

C<

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using = or < will not select the correct rows.

The > operator filters for salaries greater than 50000.

3fill in blank

hard

Fix the error in the query to count employees in each department.

SQL

SELECT department, COUNT([1]) FROM employees GROUP BY department;

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

Aemployee_id

Bdepartment

Csalary

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Counting a column that can have NULLs leads to wrong counts.

Using COUNT(*) counts all rows per department correctly.

4fill in blank

hard

Fill both blanks to create a query that lists employee names and their salaries, ordered by salary descending.

SQL

SELECT [1], [2] FROM employees ORDER BY salary DESC;

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

Aname

Bsalary

Cemployee_id

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting wrong columns will not show the expected data.

Selecting name and salary shows the requested columns.

5fill in blank

hard

Fill all three blanks to create a query that shows department, average salary, and number of employees, only for departments with more than 5 employees.

SQL

SELECT [1], AVG([2]), COUNT([3]) FROM employees GROUP BY [1] HAVING COUNT([3]) > 5;

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

Adepartment

Bsalary

C*

Demployee_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong columns in COUNT or GROUP BY causes errors or wrong results.

This query groups by department, calculates average salary, counts employees, and filters groups with more than 5 employees.