Keys (primary, candidate, foreign, super) in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to identify the key that uniquely identifies each record in a table.

DBMS Theory

The [1] key uniquely identifies each record in a database table.

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

Aforeign

Bsuper

Ccandidate

Dprimary

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing primary key with foreign key.

Thinking candidate key is always used as the main key.

The primary key is a unique identifier for each record in a table. It cannot be null and must be unique.

2fill in blank

medium

Complete the sentence to identify the key that can potentially be chosen as a primary key.

DBMS Theory

A [1] key is a minimal set of attributes that can uniquely identify a record.

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

Asuper

Bcandidate

Cforeign

Dprimary

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing candidate key with foreign key.

Assuming candidate key is always the primary key.

A candidate key is a column or set of columns that can uniquely identify rows in a table. One candidate key is chosen as the primary key.

3fill in blank

hard

Complete the sentence to identify the key that links two tables.

DBMS Theory

A [1] key is used to link two tables.

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

Aforeign

Bprimary

Ccandidate

Dsuper

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing foreign key with primary key.

Thinking foreign key must be unique.

A foreign key is a field in one table that refers to the primary key in another table, creating a link between the two tables.

4fill in blank

hard

Fill both blanks to complete the definition of a super key.

DBMS Theory

A [1] key is a set of one or more attributes that [2] uniquely identify a record in a table.

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

Asuper

Bcandidate

Ccan

Dcannot

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking super key must be minimal.

Confusing super key with foreign key.

A super key is any combination of columns that can uniquely identify a record. It can include extra attributes beyond what is necessary.

5fill in blank

hard

Fill all three blanks to complete the dictionary comprehension that selects candidate keys from a list.

DBMS Theory

candidate_keys = { [1]: [2] for [3] in keys if is_candidate([3]) }

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

Ak

Bk.upper()

Dkeys

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name in the comprehension.

Mixing up keys and values in the dictionary.

This comprehension creates a dictionary where keys are candidate keys in uppercase, and values are the original keys. The variable k iterates over keys.