SELECT with expressions and calculations in SQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the SELECT statement do in SQL?

The SELECT statement retrieves data from a database table and returns it as a result set.

beginner

How can you perform calculations in a SELECT statement?

You can use arithmetic operators like +, -, *, / directly in the SELECT clause to calculate values from columns or constants.

beginner

Example: What does this query do? <br>SELECT price, quantity, price * quantity AS total_cost FROM sales;

It selects the price and quantity columns from the sales table and calculates a new column total_cost by multiplying price and quantity for each row.

intermediate

Can you use functions in SELECT expressions? Give an example.

Yes, you can use functions like ROUND, ABS, or CONCAT in SELECT expressions. For example: <br>SELECT ROUND(price * quantity, 2) AS total_rounded FROM sales; rounds the total cost to 2 decimal places.

intermediate

What happens if you divide by zero in a SELECT calculation?

Dividing by zero causes an error in SQL. You should handle it using CASE or NULLIF to avoid errors, for example: <br>SELECT price / NULLIF(quantity, 0) AS safe_division FROM sales;

Which operator is used to multiply two columns in a SELECT statement?

A /

B +

C -

D *

The * operator multiplies values in SQL expressions.

What will this query return? <br>SELECT 10 + 5 AS sum_result;

A A list of numbers from 10 to 5

B An error because no table is specified

C A column named sum_result with value 15

D NULL

You can select expressions without a table; it returns the calculated value as a column.

How do you rename a calculated column in the result set?

A Using GROUP BY

B Using AS keyword

C Using WHERE clause

D Using ORDER BY

The AS keyword assigns an alias (name) to the calculated column.

Which function rounds a number to a specific decimal place in SQL?

A ROUND

B ABS

C CONCAT

D LENGTH

ROUND rounds numbers to the specified decimal places.

What is the result of dividing by zero in a SQL SELECT expression?

A An error occurs

B Returns zero

C Returns NULL automatically

D Returns infinity

Dividing by zero causes an error; it must be handled to avoid query failure.

Explain how to use expressions and calculations in a SELECT statement with an example.

Think about multiplying two columns and giving the result a name.

Describe how to safely handle division in SELECT expressions to avoid errors.

Consider how to avoid dividing by zero in your calculation.