What is a database in SQL - Interactive Quiz & Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to select all columns from the table named 'users'.

SQL

SELECT [1] FROM users;

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

AEVERY

B*

CALL

DALL_COLUMNS

Attempts:

3 left

💡 Hint

Common Mistakes

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

Trying to write column names when you want all columns.

The asterisk (*) means to select all columns from the table.

2fill in blank

medium

Complete the code to find the names of all customers from the 'customers' table.

SQL

SELECT [1] FROM customers;

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

Aaddress

Bphone

Cname

Dage

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting columns unrelated to the question like age or phone.

Using * when only names are needed.

We want to get the 'name' column from the customers table.

3fill in blank

hard

Fix the error in the code to select all records from the 'orders' table.

SQL

SELECT [1] orders;

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

AJOIN

BINTO

CWHERE

DFROM

Attempts:

3 left

💡 Hint

Common Mistakes

Using INTO or WHERE instead of FROM.

Omitting the keyword before the table name.

The keyword FROM is needed to specify the table to select from.

4fill in blank

hard

Fill both blanks to select the 'email' column from the 'subscribers' table where the status is 'active'.

SQL

SELECT [1] FROM subscribers WHERE status [2] 'active';

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

Aemail

B=

C!=

DLIKE

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' or 'LIKE' instead of '=' in the WHERE clause.

Selecting the wrong column.

Select the 'email' column and use '=' to filter rows where status is 'active'.

5fill in blank

hard

Fill all three blanks to select the 'product' and 'price' columns from 'inventory' where quantity is greater than 10.

SQL

SELECT [1], [2] FROM inventory WHERE quantity [3] 10;

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

Aproduct

Bprice

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' in the WHERE clause.

Selecting wrong columns or missing one.

Select 'product' and 'price' columns and filter rows where quantity is greater than 10 using '>'.

Practice

1. What is a database primarily used for?

easy

A. Writing emails

B. Designing websites

C. Storing and organizing data

D. Creating graphics

Solution

1. Step 1: Understand the purpose of a database

   A database is designed to store and organize data efficiently.

2. Step 2: Compare with other options

   Designing websites, writing emails, and creating graphics are not main functions of a database.

3. Final Answer:

   Storing and organizing data -> Option C

4. Quick Check:

   Database = Store and organize data [OK]

Hint: Databases store data, not create websites or emails [OK]

Common Mistakes:

• Confusing database with website design
• Thinking database is for email writing
• Mixing database with graphic creation

2. Which SQL command is used to create a new table in a database?

easy

A. INSERT

B. UPDATE

C. SELECT

D. CREATE

Solution

1. Step 1: Identify the command for creating tables

   The SQL command to create a new table is CREATE.

2. Step 2: Understand other commands

   INSERT adds data, SELECT retrieves data, and UPDATE modifies data, none create tables.

3. Final Answer:

   CREATE -> Option D

4. Quick Check:

   CREATE = Make new table [OK]

Hint: CREATE makes tables; INSERT adds data [OK]

Common Mistakes:

• Using INSERT to create tables
• Confusing SELECT with CREATE
• Thinking UPDATE creates tables

3. Given the table Users with columns id and name, what does this query return?

SELECT name FROM Users WHERE id = 2;

medium

A. User name with id 2

B. All user names

C. User id 2

D. Error: missing table

Solution

1. Step 1: Analyze the SELECT statement

   The query selects the name column from Users where id equals 2.

2. Step 2: Understand the WHERE clause effect

   It filters rows to only those with id = 2, so only that user's name is returned.

3. Final Answer:

   User name with id 2 -> Option A

4. Quick Check:

   SELECT name WHERE id=2 = User name [OK]

Hint: WHERE filters rows; SELECT picks columns [OK]

Common Mistakes:

• Thinking it returns all names
• Confusing id with name in output
• Assuming syntax error without reason

4. Identify the error in this SQL statement:

SELEC * FROM Customers;

medium

A. Missing table name

B. Typo in SELECT keyword

C. Incorrect use of *

D. No error

Solution

1. Step 1: Check the SQL keywords

   The keyword SELEC is misspelled; it should be SELECT.

2. Step 2: Verify other parts

   The table name Customers is present and * is correctly used to select all columns.

3. Final Answer:

   Typo in SELECT keyword -> Option B

4. Quick Check:

   SELECT typo causes error [OK]

Hint: Check spelling of SQL keywords carefully [OK]

Common Mistakes:

• Ignoring keyword typos
• Thinking * is invalid
• Assuming missing table name

5. You want to store information about books with columns id, title, and author. Which SQL command correctly creates this table?

hard

A. CREATE TABLE Books (id INT, title VARCHAR(100), author VARCHAR(100));

B. INSERT INTO Books (id, title, author);

C. SELECT id, title, author FROM Books;

D. UPDATE Books SET title = 'New Title';

Solution

1. Step 1: Identify the command to create a table

   The CREATE TABLE command defines a new table with specified columns and types.

2. Step 2: Check the syntax correctness

   CREATE TABLE Books (id INT, title VARCHAR(100), author VARCHAR(100)); correctly uses CREATE TABLE with column names and data types.

3. Step 3: Understand other commands

   INSERT INTO adds data, SELECT retrieves data, and UPDATE modifies data, none create tables.

4. Final Answer:

   CREATE TABLE Books (id INT, title VARCHAR(100), author VARCHAR(100)); -> Option A

5. Quick Check:

   CREATE TABLE defines structure [OK]

Hint: CREATE TABLE defines columns and types [OK]

Common Mistakes:

• Using INSERT to create tables
• Confusing SELECT with CREATE
• Trying to UPDATE before table exists