Composite primary keys in SQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a composite primary key on columns 'order_id' and 'product_id'.

SQL

CREATE TABLE order_details (order_id INT, product_id INT, quantity INT, PRIMARY KEY ([1]));

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Aorder_id, product_id

Bproduct_id

Corder_id

Dquantity

Attempts:

3 left

💡 Hint

Common Mistakes

Using only one column as primary key instead of both.

Including columns that are not part of the key.

The composite primary key must include both 'order_id' and 'product_id' together to uniquely identify each row.

2fill in blank

medium

Complete the code to add a composite primary key constraint named 'pk_enrollment' on 'student_id' and 'course_id'.

SQL

ALTER TABLE enrollments ADD CONSTRAINT pk_enrollment [1] (student_id, course_id);

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ACHECK

BPRIMARY KEY

CUNIQUE

DFOREIGN KEY

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'FOREIGN KEY' instead of 'PRIMARY KEY'.

Using 'UNIQUE' which allows NULLs.

The constraint to define a composite primary key is 'PRIMARY KEY'.

3fill in blank

hard

Fix the error in the composite primary key definition by completing the code.

SQL

CREATE TABLE attendance (student_id INT, class_id INT, date DATE, PRIMARY KEY [1]);

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A{student_id, class_id}

B[student_id, class_id]

Cstudent_id, class_id

D(student_id, class_id)

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting parentheses causes syntax errors.

Using square brackets or curly braces instead of parentheses.

The columns in a PRIMARY KEY must be enclosed in parentheses.

4fill in blank

hard

Fill both blanks to create a table 'subscriptions' with a composite primary key on 'user_id' and 'service_id'.

SQL

CREATE TABLE subscriptions (user_id INT, service_id INT, start_date DATE, [1] PRIMARY KEY [2]);

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ACONSTRAINT sub_pk

BFOREIGN KEY

C(user_id, service_id)

DUNIQUE

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'FOREIGN KEY' instead of 'PRIMARY KEY'.

Not enclosing columns in parentheses.

Use 'CONSTRAINT sub_pk' to name the primary key, followed by the columns in parentheses.

5fill in blank

hard

Fill all three blanks to define a composite primary key named 'pk_order_item' on 'order_id' and 'item_id' in the 'order_items' table.

SQL

CREATE TABLE order_items (order_id INT, item_id INT, quantity INT, [1] pk_order_item [2] [3] (order_id, item_id));

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ACONSTRAINT

BPRIMARY

CKEY

DFOREIGN

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'FOREIGN' instead of 'PRIMARY'.

Omitting 'CONSTRAINT' keyword.

The correct syntax is: CONSTRAINT pk_order_item PRIMARY KEY (order_id, item_id).