What Are Functions?3:12 with Andrew Chalkley
You've seen keywords and operators, now it's time to see a new concept in the SQL programming language: functions.
Keywords: Commands issued to a database. The data presented in queries is unaltered.
Operators: Performs comparisons and simple manipulation
Functions: Presents data differently through more complex manipulation
A function looks like:
<function name>(<value or column>)
[MUSIC] 0:00 Throughout this course, we're going to use some things that look like SQL keywords 0:05 but are different in a key way. 0:08 They're called functions. 0:10 Functions are different from normal keywords because they can manipulate 0:13 the results of a query in different ways. 0:17 Also, they aren't restricted to being used in just one part of a query. 0:20 But before I fully explain functions, 0:25 let's review some of the syntax definition you already know. 0:28 A key word is a command you issue to a database to do something. 0:32 The data in the results isn't altered, generally you'll see them in all caps. 0:36 Then we have operators. 0:42 You've seen operators that perform simple actions for comparisons. 0:44 They can also be used for 0:48 simple manipulation tasks, I'll introduce you to some later. 0:49 Then there's functions. 0:54 This may be a new concept to you. 0:56 They are like keywords, as they have names and they do tell databases to do things. 0:59 When you've used the select statement up until now, the data in the database 1:04 is simply returned in the same format as it appears in the database. 1:08 Functions, on the other hand, transform the results. 1:13 Functions are used for more complex operations, such as making a string 1:16 all uppercase, or getting the sum of all numbers in a particular column. 1:20 The underlying data in the table isn't changed. 1:25 Just the presentation is different. 1:28 We'll look at lots of functions in this course. 1:31 Let's take a look at what the function looks like. 1:34 The function name, generally in upper case, 1:37 a pair of parenthesis and then the data or the column of data you want transforming. 1:41 What's presented to you when the SQL query is executed is the transformed or 1:47 modified data. 1:52 Let's quickly look at a real life example 1:54 of using a function to uppercase a string of text. 1:56 Many official documents like your passport or 2:00 government issued ID cards has your name in uppercase. 2:03 Your name is in a database somewhere and it may not be in uppercase. 2:07 So let say you want to uppercase the string of my name, Andrew Chalkley. 2:11 We'd put that in parenthesis and then use the function named upper. 2:17 This creates a new string of Andrew Chalkley all in uppercase. 2:23 Let's see this in context of the SQL query. 2:28 Here's a regular query without any functions, 2:31 here's the results of that query. 2:34 Once we use a function, the results change. 2:37 We look at this function again with some more examples later. 2:39 There are differences in functions and 2:46 operators between different relational database systems. 2:48 SQL playground runs a version of SQLite under the hood. 2:51 What works in SQLite might not work the same in MySQL, PostgreSQL or SQL server. 2:54 Many of the functions and operators we're using are universal. 3:00 However, check the teacher's notes with every video for any differences and 3:04 gotchas in other database implementations. 3:08
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