Why JOINs combine related tables in MySQL - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

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

MySQL

SELECT [1] FROM employees;

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

A*

Ball

Ceverything

Dcolumns

Attempts:

3 left

💡 Hint

Common Mistakes

Writing 'all' instead of '*'

Using 'columns' which is not valid SQL syntax

The asterisk (*) means select all columns from the table.

2fill in blank

medium

Complete the code to join the employees table with the departments table on department_id.

MySQL

SELECT employees.name, departments.name FROM employees [1] departments ON employees.department_id = departments.department_id;

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AUNION

BJOIN

CWHERE

DGROUP BY

Attempts:

3 left

💡 Hint

Common Mistakes

Using WHERE instead of JOIN for combining tables

Using UNION which combines result sets vertically

The JOIN keyword combines rows from two tables based on a related column.

3fill in blank

hard

Fix the error in the JOIN clause to correctly combine employees and departments.

MySQL

SELECT employees.name, departments.name FROM employees JOIN departments [1] employees.department_id = departments.department_id;

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AWHERE

BUSING

CWITH

DON

Attempts:

3 left

💡 Hint

Common Mistakes

Using WHERE instead of ON in JOIN clause

Using WITH which is not valid here

The ON keyword specifies the condition for the JOIN to combine related rows.

4fill in blank

hard

Fill both blanks to select employee names and their department names using an INNER JOIN.

MySQL

SELECT employees.name AS [1], departments.name AS [2] FROM employees INNER JOIN departments ON employees.department_id = departments.department_id;

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Aemployee_name

Bdepartment_name

Cemp_name

Ddept_name

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same alias for both columns

Using unclear or confusing aliases

Aliases help rename columns in the output for clarity.

5fill in blank

hard

Fill all three blanks to create a query that selects employee names, department names, and filters for departments with 'Sales' in the name.

MySQL

SELECT employees.name AS [1], departments.name AS [2] FROM employees JOIN departments ON employees.department_id = departments.department_id WHERE departments.name [3] '%Sales%';

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

Aemp_name

Bdept_name

CLIKE

DIN

Attempts:

3 left

💡 Hint

Common Mistakes

Using IN instead of LIKE for pattern matching

Not using aliases for selected columns

The LIKE operator is used to filter text patterns in SQL.