Types of databases (relational, NoSQL, object-oriented) in DBMS Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all columns from a relational database table named 'employees'.

DBMS Theory

SELECT [1] FROM employees;

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

AALL_COLUMNS

BALL

CEVERY

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using words like ALL or EVERY instead of the symbol *.

Trying to write the column names manually when all columns are needed.

In SQL, * means select all columns from the table.

2fill in blank

medium

Complete the code to insert a document into a NoSQL database collection named 'users'.

DBMS Theory

db.users.insertOne({ name: 'Alice', age: [1] });

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

A'25'

B25

C"25"

Dtwentyfive

Attempts:

3 left

💡 Hint

Common Mistakes

Putting numbers inside quotes, which makes them strings.

Writing age as a word instead of a number.

In NoSQL databases like MongoDB, numbers are written without quotes.

3fill in blank

hard

Fix the error in the object-oriented database query to retrieve all objects of class 'Car'.

DBMS Theory

SELECT * FROM [1];

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ACar

Bcar

CCAR

Dcars

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase class names which may cause errors.

Using plural form instead of the class name.

Class names in object-oriented databases are case-sensitive and usually start with a capital letter.

4fill in blank

hard

Fill both blanks to create a NoSQL query that finds users older than 30.

DBMS Theory

db.users.find({ age: { [1]: [2] } });

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

A$gt

B$lt

C30

D25

Attempts:

3 left

💡 Hint

Common Mistakes

Using $lt which means 'less than' instead of 'greater than'.

Using the wrong number for the age condition.

In NoSQL queries, $gt means 'greater than'. We want users older than 30, so age > 30.

5fill in blank

hard

Fill all three blanks to create an SQL query that selects the 'name' and 'price' columns from the 'products' table where price is less than 100.

DBMS Theory

SELECT [1], [2] FROM products WHERE price [3] 100;

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

Aname

Bprice

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using the greater than operator > instead of less than.

Swapping the column names or missing one.

We select columns 'name' and 'price' and filter rows where price is less than 100 using <.