Primary key declaration in MySQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a primary key on the 'id' column.

MySQL

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

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AINDEX

BFOREIGN KEY

CUNIQUE

DPRIMARY KEY

Attempts:

3 left

💡 Hint

Common Mistakes

Using FOREIGN KEY instead of PRIMARY KEY

Using UNIQUE without PRIMARY KEY

Forgetting to specify any key constraint

The PRIMARY KEY constraint uniquely identifies each record in the table.

2fill in blank

medium

Complete the code to declare a primary key on the 'order_id' column in this table.

MySQL

CREATE TABLE orders (order_id INT [1], order_date DATE);

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AUNIQUE

BPRIMARY KEY

CCHECK

DDEFAULT

Attempts:

3 left

💡 Hint

Common Mistakes

Using UNIQUE instead of PRIMARY KEY

Using CHECK constraint incorrectly

Not specifying any key constraint

The PRIMARY KEY constraint ensures each order_id is unique and not null.

3fill in blank

hard

Fix the error in this table creation by correctly declaring the primary key.

MySQL

CREATE TABLE products (product_id INT, name VARCHAR(50), [1] (product_id));

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APRIMARY KEY

BFOREIGN KEY

CUNIQUE

DCHECK

Attempts:

3 left

💡 Hint

Common Mistakes

Using FOREIGN KEY instead of PRIMARY KEY

Using UNIQUE constraint without PRIMARY KEY

Using CHECK constraint incorrectly

The PRIMARY KEY constraint must be declared to uniquely identify product_id.

4fill in blank

hard

Fill both blanks to declare a composite primary key on 'student_id' and 'course_id'.

MySQL

CREATE TABLE enrollments (student_id INT, course_id INT, [1] (student_id, [2]));

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APRIMARY KEY

Bcourse_id

CFOREIGN KEY

DUNIQUE

Attempts:

3 left

💡 Hint

Common Mistakes

Using FOREIGN KEY instead of PRIMARY KEY

Listing only one column in the key

Using UNIQUE instead of PRIMARY KEY

A composite primary key uses PRIMARY KEY and lists both columns inside parentheses.

5fill in blank

hard

Fill all three blanks to declare a primary key on 'id' and add a unique constraint on 'email'.

MySQL

CREATE TABLE users (id INT [1], email VARCHAR(100) [2], [3] (email));

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APRIMARY KEY

BUNIQUE

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing PRIMARY KEY and UNIQUE keywords incorrectly

Forgetting to declare unique constraint on email

Using FOREIGN KEY instead of UNIQUE

The 'id' column is declared as PRIMARY KEY, 'email' column has a UNIQUE constraint, and the table-level unique constraint is declared on 'email'.