Column aliases in MySQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a column alias in SQL?

A column alias is a temporary name given to a column in the result set of a query to make the output easier to read or understand.

beginner

How do you assign a column alias in a SELECT statement?

You use the AS keyword followed by the alias name after the column name, like: SELECT column_name AS alias_name FROM table;

intermediate

Can you use column aliases without the AS keyword?

Yes, in many SQL databases including MySQL, you can write the alias directly after the column name with a space, like: SELECT column_name alias_name FROM table;

beginner

Why use column aliases in SQL queries?

Column aliases make output easier to read, especially when columns have complex names or expressions. They also help when combining columns or using functions.

intermediate

Give an example of a column alias with a calculation.

Example: SELECT price, quantity, price * quantity AS total_cost FROM sales; This shows total_cost as the alias for the calculation.

Which keyword is commonly used to assign a column alias in SQL?

A ALIAS

B AS

C RENAME

D LABEL

The AS keyword is used to assign a column alias in SQL, for example: SELECT column_name AS alias_name.

What will this query return? SELECT price * quantity AS total FROM sales;

A A column named total with the product of price and quantity

B An error because AS cannot be used with calculations

C The original price column only

D The original quantity column only

The query returns a column named total which contains the result of price multiplied by quantity.

Is this query valid in MySQL? SELECT name full_name FROM users;

A No, alias must be in quotes

B No, AS is required

C No, alias must be after FROM

D Yes, alias without AS is allowed

MySQL allows column aliases without the AS keyword, so this query is valid.

Why might you use a column alias in a query?

A To make column names easier to understand in the output

B To change the actual column name in the table

C To delete a column from the table

D To create a new table

Column aliases only change the name shown in the query result, making it easier to read.

Which of these is a correct way to alias a column?

A SELECT age ASuser_age FROM people;

B SELECT age user_age FROM people;

C Both B and D

D SELECT age AS user_age FROM people;

Both 'AS' keyword and direct alias without AS are valid ways to assign column aliases in MySQL.

Explain what a column alias is and how to use it in a SQL SELECT query.

Think about giving a temporary name to a column in your query output.

Describe why column aliases are helpful when working with SQL queries.

Consider how query results look to someone reading them.