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Throughout this course, we're going to use some things that look like SQL keywords

but are different in a key way.

They're called functions.

Functions are different from normal keywords because they can manipulate

the results of a query in different ways.

Also, they aren't restricted to being used in just one part of a query.

But before I fully explain functions,

let's review some of the syntax definition you already know.

A key word is a command you issue to a database to do something.

The data in the results isn't altered, generally you'll see them in all caps.

Then we have operators.

You've seen operators that perform simple actions for comparisons.

They can also be used for

simple manipulation tasks, I'll introduce you to some later.

Then there's functions.

This may be a new concept to you.

They are like keywords, as they have names and they do tell databases to do things.

When you've used the select statement up until now, the data in the database

is simply returned in the same format as it appears in the database.

Functions, on the other hand, transform the results.

Functions are used for more complex operations, such as making a string

all uppercase, or getting the sum of all numbers in a particular column.

The underlying data in the table isn't changed.

Just the presentation is different.

We'll look at lots of functions in this course.

Let's take a look at what the function looks like.

The function name, generally in upper case,

a pair of parenthesis and then the data or the column of data you want transforming.

What's presented to you when the SQL query is executed is the transformed or

modified data.

Let's quickly look at a real life example

of using a function to uppercase a string of text.

Many official documents like your passport or

government issued ID cards has your name in uppercase.

Your name is in a database somewhere and it may not be in uppercase.

So let say you want to uppercase the string of my name, Andrew Chalkley.

We'd put that in parenthesis and then use the function named upper.

This creates a new string of Andrew Chalkley all in uppercase.

Let's see this in context of the SQL query.

Here's a regular query without any functions,

here's the results of that query.

Once we use a function, the results change.

We look at this function again with some more examples later.

There are differences in functions and

operators between different relational database systems.

SQL playground runs a version of SQLite under the hood.

What works in SQLite might not work the same in MySQL, PostgreSQL or SQL server.

Many of the functions and operators we're using are universal.

However, check the teacher's notes with every video for any differences and

gotchas in other database implementations.