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Review
4. First, a quick review
So you think you can count?
Rounding functions and more
Review and practice

## Instruction

Before we continue, let's review what we already know about numbers. Integers are expressed in the following way: 1, 2, 43, -27, etc. Fractions are expressed with a dot (.): 12.45, -401.238, etc. Please note that in some languages, you use a comma instead of a dot, but not in SQL! For example, 12,45 is incorrect.

In PostgreSQL (and in most programming languages) there are three kinds of numbers:

• Integer (integer): stores integers (e.g., -5, 0, 5, 42).
• Floating-point (real, double precision): stores fractions by approximating them in binary.
• Decimal (numeric): stores fractions in decimal format.

In this part, we'll discuss some of the differences between PostgreSQL's number data types.

Of course, you can use the four basic mathematical operations (add +, subtract -, multiply *, and divide /) with actual numbers in PostgreSQL. You can also use columns and constant numbers together. Take a look at the example below:

SELECT hp / 4 AS quarter_hp
FROM character;


## Exercise

For each character, display its name, level, and the sum of its hp and mp as the hmp column.

### Stuck? Here's a hint!

You can add values of two columns with a plus (+).