Why understanding relationships matters 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*

Cemployees

Dcolumns

Attempts:

3 left

💡 Hint

Common Mistakes

Using the table name instead of '*' to select all columns.

Using 'ALL' which is not valid in this context.

The asterisk (*) selects all columns from the table.

2fill in blank

medium

Complete the code to join the orders table with customers on customer_id.

SQL

SELECT orders.order_id, customers.name FROM orders JOIN customers ON orders.[1] = customers.customer_id;

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

Acustomer_id

Border_id

Cname

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using order_id instead of customer_id for the join condition.

Using a column that does not exist in the orders table.

We join on the customer_id column which links orders to customers.

3fill in blank

hard

Fix the error in the join condition to correctly link products and categories.

SQL

SELECT products.name, categories.name FROM products JOIN categories ON products.[1] = categories.id;

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

Aname

Bproduct_id

Cid

Dcategory_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using products.id instead of products.category_id.

Using categories.name instead of categories.id.

The products table has a category_id column that links to categories.id.

4fill in blank

hard

Fill both blanks to create a query that finds all orders with their customer's name.

SQL

SELECT orders.order_id, customers.[1] FROM orders JOIN customers ON orders.[2] = customers.customer_id;

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

Aname

Border_id

Ccustomer_id

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using orders.order_id instead of customers.name.

Joining on orders.order_id instead of orders.customer_id.

We select customers.name and join on orders.customer_id = customers.customer_id.

5fill in blank

hard

Fill all three blanks to select product names and their category names where category id is greater than 5.

SQL

SELECT products.[1], categories.[2] FROM products JOIN categories ON products.[3] = categories.id WHERE categories.id > 5;

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

Aname

Bcategory_id

Dproduct_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using product_id instead of category_id for the join.

Selecting wrong columns that do not exist.

We select products.name and categories.name, joining on products.category_id = categories.id.