Database design best practices in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a table with a primary key.

SQL

CREATE TABLE users (id INT [1] PRIMARY KEY, name VARCHAR(100));

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

AAUTO_INCREMENT

BUNIQUE

CNOT NULL

DDEFAULT

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE alone does not auto-generate values.

NOT NULL only prevents nulls but does not auto-increment.

The AUTO_INCREMENT keyword automatically generates unique values for the primary key column.

2fill in blank

medium

Complete the code to add a foreign key constraint.

SQL

ALTER TABLE orders ADD CONSTRAINT fk_user_id FOREIGN KEY (user_id) [1] users(id);

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

AJOINS

BLINKS

CCONNECTS

DREFERENCES

Attempts:

3 left

💡 Hint

Common Mistakes

Using LINKS or CONNECTS are not valid SQL keywords.

JOINS are used in queries, not in constraints.

The REFERENCES keyword defines the foreign key relationship to another table's column.

3fill in blank

hard

Fix the error in the table creation by completing the code.

SQL

CREATE TABLE products (product_id INT PRIMARY KEY, price [1] DECIMAL(10, 2));

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

AUNIQUE

BAUTO_INCREMENT

CNOT NULL

DDEFAULT

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE on price is not typical.

AUTO_INCREMENT is only for integer keys.

The NOT NULL constraint ensures the price column cannot be empty.

4fill in blank

hard

Fill both blanks to create a normalized table with a unique constraint.

SQL

CREATE TABLE employees (emp_id INT PRIMARY KEY, email VARCHAR(255) [1] [2]);

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

AUNIQUE

BNOT NULL

CDEFAULT

DAUTO_INCREMENT

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting NOT NULL allows empty emails.

Missing UNIQUE allows duplicate emails.

The NOT NULL constraint ensures email is always provided, and UNIQUE prevents duplicate emails.

5fill in blank

hard

Fill all three blanks to create a table with a composite primary key and a foreign key.

SQL

CREATE TABLE enrollment (student_id INT, course_id INT, semester VARCHAR(10), PRIMARY KEY ([1], [2]), FOREIGN KEY (student_id) [3] students(id));

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

Astudent_id

Bcourse_id

CREFERENCES

Dsemester

Attempts:

3 left

💡 Hint

Common Mistakes

Using semester as part of the primary key is not typical here.

Forgetting REFERENCES causes foreign key errors.

The composite primary key uses student_id and course_id. The foreign key uses REFERENCES to link to the students table.