Primary keys and foreign keys in Supabase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a primary key for the 'users' table.

Supabase

CREATE TABLE users (id SERIAL [1] PRIMARY KEY, name TEXT);

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AUNIQUE

BCHECK

CDEFAULT

DNOT NULL

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE alone does not prevent NULL values.

Forgetting to specify NOT NULL on primary key columns.

The primary key column must be NOT NULL to ensure uniqueness and identification.

2fill in blank

medium

Complete the code to create a foreign key in the 'orders' table referencing 'users'.

Supabase

CREATE TABLE orders (order_id SERIAL PRIMARY KEY, user_id INTEGER [1] REFERENCES users(id));

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AUNIQUE

BNOT NULL

CDEFAULT

DCHECK

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving foreign key columns nullable when they should not be.

Using UNIQUE instead of NOT NULL.

The foreign key column should be NOT NULL to ensure every order is linked to a user.

3fill in blank

hard

Fix the error in the foreign key constraint syntax.

Supabase

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

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AREFERENCES

BREFERENCING

CREFERENCE

DREFERS

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'REFERENCE' instead of 'REFERENCES'.

Misspelling the keyword causes syntax errors.

The correct keyword to link a foreign key is REFERENCES.

4fill in blank

hard

Fill both blanks to create a table with a composite primary key.

Supabase

CREATE TABLE enrollment (student_id INTEGER [1], course_id INTEGER [2], PRIMARY KEY (student_id, course_id));

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ANOT NULL

BUNIQUE

CDEFAULT

DCHECK

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving one or both columns nullable.

Using UNIQUE instead of NOT NULL.

Both columns in a composite primary key must be NOT NULL to ensure uniqueness.

5fill in blank

hard

Fill all three blanks to create a foreign key with ON DELETE CASCADE and ON UPDATE CASCADE.

Supabase

ALTER TABLE orders ADD CONSTRAINT fk_user FOREIGN KEY (user_id) [1] users(id) ON DELETE [2] ON UPDATE [3];

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AREFERENCES

BCASCADE

CRESTRICT

DSET NULL

Attempts:

3 left

💡 Hint

Common Mistakes

Using RESTRICT or SET NULL instead of CASCADE for ON DELETE or ON UPDATE.

Misspelling REFERENCES.

Use REFERENCES to define the foreign key, and CASCADE to automatically update or delete related rows.