Why aggregation summarizes data in MySQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to count the number of employees in the table.

MySQL

SELECT COUNT([1]) FROM employees;

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

Aname

Bemployee_id

C*

Dsalary

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT with a specific column may miss NULL values.

Forgetting to use COUNT function.

The COUNT(*) function counts all rows in the table, summarizing the total number of employees.

2fill in blank

medium

Complete the code to find the average salary of employees.

MySQL

SELECT AVG([1]) FROM employees;

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Aemployee_id

Bsalary

Cname

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Using AVG on non-numeric columns.

Using SUM instead of AVG.

The AVG(salary) function calculates the average salary, summarizing the salary data.

3fill in blank

hard

Fix the error in the code to get the total salary paid to employees.

MySQL

SELECT [1](salary) FROM employees;

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

ASUM

BCOUNT

CAVG

DMAX

Attempts:

3 left

💡 Hint

Common Mistakes

Using COUNT instead of SUM.

Using AVG when total sum is needed.

The SUM(salary) function adds all salaries together, summarizing total payment.

4fill in blank

hard

Fill both blanks to find the maximum and minimum salaries.

MySQL

SELECT [1](salary) AS max_salary, [2](salary) AS min_salary FROM employees;

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

AMAX

BMIN

CSUM

DAVG

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up MAX and MIN functions.

Using SUM or AVG instead of MAX or MIN.

MAX(salary) finds the highest salary, and MIN(salary) finds the lowest salary, summarizing salary range.

5fill in blank

hard

Fill all three blanks to get the count, average, and total salary for employees.

MySQL

SELECT [1](*) AS total_employees, [2](salary) AS average_salary, [3](salary) AS total_salary FROM employees;

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

ACOUNT

BAVG

CSUM

DMAX

Attempts:

3 left

💡 Hint

Common Mistakes

Using MAX instead of SUM for total salary.

Using COUNT on salary instead of COUNT(*).

This query counts employees, calculates average salary, and sums total salary, summarizing key data points.