Column aliases with AS in SQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Output of column alias in SELECT

What is the output of this SQL query?

SELECT first_name AS name FROM employees;

Assume the employees table has these rows:

first_name
John
Jane
Bob

SQL

SELECT first_name AS name FROM employees;

A

name
John
Jane
Bob

B

name
first_name
first_name

C

first_name
John
Jane
Bob

D Error: Invalid column alias

💡 Hint

The AS keyword renames the column in the output.

Using AS changes the column header in the result to the alias name.

❓ query_result

intermediate

Multiple column aliases in SELECT

What is the output of this SQL query?

SELECT first_name AS fname, last_name AS lname FROM employees;

Assume employees table rows:

first_name | last_name
Alice      | Smith
Bob        | Brown

SQL

SELECT first_name AS fname, last_name AS lname FROM employees;

A

first_name | last_name
Alice      | Smith
Bob        | Brown

B

fname | lname
Alice | Smith
Bob   | Brown

C

fname | last_name
Alice | Smith
Bob   | Brown

D Error: AS keyword used incorrectly

💡 Hint

Each column alias changes the column header separately.

Both columns are renamed in the output using AS.

📝 Syntax

advanced

Identify the syntax error with AS alias

Which option contains a syntax error when using column alias with AS?

A SELECT salary AS monthly_salary FROM payroll;

B SELECT city AS location FROM addresses;

C SELECT age AS FROM users;

D SELECT price AS cost FROM products;

💡 Hint

AS must be followed by a valid alias name.

Option C misses the alias name after AS, causing syntax error.

❓ query_result

advanced

Effect of alias on ORDER BY clause

What is the output order of this query?

SELECT first_name AS name FROM employees ORDER BY name DESC;

Employees table:

first_name
Anna
Zack
Mike

SQL

SELECT first_name AS name FROM employees ORDER BY name DESC;

A

name
Zack
Mike
Anna

B

name
Anna
Mike
Zack

C

first_name
Anna
Zack
Mike

D Error: Cannot use alias in ORDER BY

💡 Hint

Aliases can be used in ORDER BY to sort results.

The query orders by the alias 'name' in descending order.

🧠 Conceptual

expert

Why use column aliases with AS?

Which is the best reason to use column aliases with AS in SQL queries?

A To speed up query execution by indexing aliases

B To change the data type of a column in the table

C To permanently rename columns in the database schema

D To rename columns in the output for clarity or formatting

💡 Hint

Think about what aliases affect: output or schema?

Aliases only rename columns in the query result, not the table.