SQL Server 2008 Essential Training
Illustration by Mark Todd

Introduction to SQL functions


SQL Server 2008 Essential Training

with Simon Allardice

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Video: Introduction to SQL functions

Earlier we saw a few examples of what are called aggregate functions in SQL, like using COUNT to return the total number of rows in a table or using MAX to return in the largest value in a particular column, or average or SUM or MIN. These functions, like in other languages, are just a way of packaging up a piece of useful behavior and giving it a name, so that we can use it again-and-again. When you're writing these in SQL Server Management Studio they tend to show up in hot pink.
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  1. 2m 21s
    1. Welcome
      1m 19s
    2. Using the exercise files
      1m 2s
  2. 17m 58s
    1. SQL Server core concepts
      9m 4s
    2. SQL Server editions
      3m 8s
    3. Applications included with SQL Server
      5m 46s
  3. 26m 1s
    1. Preparing for installation
      3m 44s
    2. Creating service accounts
      2m 33s
    3. Installing SQL Server
      11m 42s
    4. Post-installation checks
      3m 9s
    5. Installing sample databases
      4m 53s
  4. 13m 35s
    1. Introduction to SQL Server Management Studio
      8m 7s
    2. Introduction to SQL Server Books Online
      3m 6s
    3. SQL Server system databases
      2m 22s
  5. 1h 26m
    1. Planning your database
      9m 39s
    2. Creating a SQL Server database
      4m 7s
    3. Creating tables
      7m 51s
    4. Data types in SQL Server
      12m 25s
    5. Defining keys
      8m 9s
    6. Creating default values
      4m 39s
    7. Creating check constraints
      2m 25s
    8. Creating unique constraints
      4m 34s
    9. Introduction to relationships and foreign keys
      9m 51s
    10. Creating relationships in SQL Server Management Studio
      8m 14s
    11. Database normalization
      11m 47s
    12. Creating computed columns
      3m 10s
  6. 23m 11s
    1. Using the SQL Server Import and Export Wizard
      3m 58s
    2. Importing Excel files into SQL Server
      6m 11s
    3. Importing CSV files into SQL Server
      5m 27s
    4. Importing Access databases into SQL Server
      7m 35s
  7. 55m 29s
    1. Introduction to Transact-SQL
      3m 43s
    2. Using SELECT statements
      7m 16s
    3. Changing the default database
      2m 21s
    4. Creating conditions in SQL
      8m 10s
    5. Sorting your output
      3m 23s
    6. Using aggregate functions
      7m 12s
    7. Finding unique values
      2m 14s
    8. Using subqueries
      9m 33s
    9. Joining multiple tables together
      8m 0s
    10. Viewing execution plans
      3m 37s
  8. 19m 36s
    1. Writing INSERT statements
      5m 47s
    2. Writing UPDATE statements
      4m 38s
    3. Writing DELETE statements
      2m 54s
    4. Using the OUTPUT clause to return inserted keys and GUIDs
      6m 17s
  9. 32m 52s
    1. Introduction to SQL functions
      6m 26s
    2. Using SQL configuration functions
      2m 14s
    3. Using string functions
      7m 26s
    4. Using date functions
      6m 27s
    5. Creating user-defined functions
      10m 19s
  10. 28m 46s
    1. Introduction to stored procedures
      4m 23s
    2. Creating stored procedures
      11m 23s
    3. Introducing transactions
      4m 23s
    4. Creating transactions
      8m 37s
  11. 16m 39s
    1. Understanding and creating indexes
      6m 32s
    2. Monitoring and rebuilding indexes
      6m 0s
    3. Monitoring database size and integrity
      4m 7s
  12. 11m 41s
    1. Creating backups
      4m 21s
    2. Creating differential backups and using backup compression
      3m 40s
    3. Restoring databases
      3m 40s
  13. 17m 40s
    1. Introduction to SQL Server security and permissions
      5m 54s
    2. Adding a Windows user to the database
      5m 7s
    3. Creating SQL Server logins and switching authentication modes
      6m 39s
  14. 36m 41s
    1. Introduction to SQL Server Reporting Services
      2m 52s
    2. Connecting to the Report Manager
      4m 29s
    3. Using Report Builder
      12m 4s
    4. Formatting values in reports
      4m 17s
    5. Adding indicators to reports
      5m 11s
    6. Adding charts to reports
      3m 54s
    7. Working with report security
      3m 54s
  15. 24m 41s
    1. Introduction to SQL Server Integration Services (SSIS)
      1m 57s
    2. Using Business Intelligence Development Studio (BIDS)
      6m 59s
    3. Creating and executing a simple SSIS package
      7m 35s
    4. Importing packages into SQL Server Management Studio
      3m 21s
    5. Scheduling jobs with SQL Server Agent
      4m 49s
  16. 31s
    1. Goodbye

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Watch the Online Video Course SQL Server 2008 Essential Training
6h 54m Beginner Dec 15, 2010

Viewers: in countries Watching now:

In SQL Server 2008 Essential Training, Simon Allardice explores all the major features of SQL Server 2008 R2, beginning with core concepts: installing, planning, and building a first database. Explore how Transact-SQL is used to retrieve, update, and insert information, and gain insight into how to effectively administer databases. The course also covers features outside SQL Server's database engine, including technologies that have grown up around it: SQL Server Reporting Services and Integration Services. Exercise files are included with the course.

Topics include:
  • Using T-SQL (Transact-SQL)
  • Managing databases with SQL Server Management Studio
  • Understanding database normalization
  • Using SELECT statements
  • Building indexes
  • Monitoring database size and integrity
  • Backing up and restoring databases
  • Creating functions and stored procedures
  • Managing database permissions
  • Creating and formatting reports
  • Adding charts to reports
  • Creating and executing a simple SSIS package
Business Developer IT
SQL Server
Simon Allardice

Introduction to SQL functions

Earlier we saw a few examples of what are called aggregate functions in SQL, like using COUNT to return the total number of rows in a table or using MAX to return in the largest value in a particular column, or average or SUM or MIN. These functions, like in other languages, are just a way of packaging up a piece of useful behavior and giving it a name, so that we can use it again-and-again. When you're writing these in SQL Server Management Studio they tend to show up in hot pink.

We do have a few other aggregate functions, but these are really just the tip of the iceberg, because SQL Server has over 200 functions. But don't worry. You don't need to go and memorize every single one of them, because although some of these 200 things, like COUNT and MAX and MIN, are so common and so useful that you could end up using them on almost a daily basis, some functions are specialized enough that you might work with SQL Server for years and never come across them. But they're all packaged behavior, packaged operations.

So a simple and common operation like return the total number of rows becomes packaged up as the COUNT function and we can use it again-and-again. But we also have operations like "Return the angle in radians between the positive x-axis and the ray from the origin to the (y, x), where x and y are the values of the two specified float expressions." And that is also packaged up inside SQL as the ATN2 or arctangent function. But just between you and me, I've been working with SQL Server for over ten years and I've never needed this one.

So how do we get familiar with the good and the useful ones? I'm going to go through some of my favorite functions and show you how to use them. But like so many other things, treat Books Online as your friend and companion here. If you open up Books Online and go to the Index, you'll be able to look for the word Functions. Now when you do this, you're going to see them show up in many different areas. Functions for ODBC, SQL Server. There will be quite a few, depending on what you're filtering on. In fact the one that I'm interested in, is actually functions Transact-SQL, so functions for T-SQL, because it's a bit more specific and it gets down to the functions quicker.

And this page, I quite like this one, so I'm going to click somewhere in the page so that the Favorite button becomes active and I'll add that to my list of favorite, so I can come back to this whenever I need to. The functions are grouped. We have the Aggregate Functions here and I can drop-down and explore things like the Count function and see how it's meant to be used. Click back a couple of times, I've also got configuration functions, things like the server name and the version, mathematical function, signs and cosigns if I need those, security and string functions for working with the text.

And I can drill down into each of them and see examples and read about exactly how to use them. Now the thing about functions is they're actually stored as part of your database. In fact if I connect to my SQL Server instance and drill down into any of these databases, like AdventuresWorksLT, I'll find that each database has a Programmability folder and each of those has a Functions folder and each of those has a Systems Functions folder. And what I'm going to find here is a list just presented differently of the same available functions.

The aggregate functions that we have, the configuration, the date and time, the mathematical functions. And it can be useful to have these showing up in SQL Server just to take a quick look at what's available. Remind yourself what the name is for example. Now you'll see that most functions have the parentheses after them, and that's how they're called. We've seen examples using COUNT, passing in the star and parentheses, using average, passing in ListPrice, but you'll find even when you're not passing something in those parentheses, you still need them.

There is a very popular function called GETDATE, but when you use it you need the two parentheses even if it's empty. Now there are a few functions that just use the name of the function with no parentheses. If you're into geek trivia this is what's known as an Niladic function. Most of the functions without parentheses are easy to recognize because they have two @ signs in front of them. Although there are three or four little odd ones that don't like CURRENT_USER. It doesn't have parentheses and it doesn't have @ signs.

The two @ signs aren't magical. They're just a way of marking a few of these functions. In fact most of the ones with @ signs, if you see them in SQL Server Management Studio, you'll find them in the Configuration section and there are things like the version of the server. The server name, the language of the current server, the option set on it. The thing is you don't want to get worried about whether the two @ signs are there or whether the parentheses are there, because there is an easy answer. If you see the function in SQL Server Management Studio or in Books Online and it has parentheses, then you use parentheses. If it doesn't then you don't, end of story.

But the thing about all of these functions is that they give you a value back. COUNT gives me back an integer that represents the number of rows in that table. Average, well that gives me back whatever I passed into it. If ListPrice was a money column then I get a money average back. If it was an integer I get an integer back. If I used the GETDATE function I will get a date-time value back. If I used the @@LANGUAGE function I get a varchar back with, in this case US_English.

If I called the CURRENT_USER function, well depending on how my database is configured, I may get dbo. That will be a very common response from that. A few functions can return several results and that would usually be in the form of the table. But most functions are like these. They return what's called a scalar value. This is an old computing term for a single value. COUNT is a function that returns one integer. GETDATE returns one date time value. They don't return a collection, they don't return an array. They return one scalar value.

So how do you use these functions? Well we've seen functions used in SELECt statements and that's very, very common but they can be used in WHERE clauses, in UPDATEs, INSERTs, all over the place. So next I'll take you through a few of them.

Find answers to the most frequently asked questions about SQL Server 2008 Essential Training .

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Q: I'm having problems installing the free Express R2 version of SQL Server on Windows XP. I tried 64-bit and 32-bit versions. In the videos, the author installs from a DVD. Do I need to do the same?
A: While the author installs from a DVD, it's not strictly necessary. There certainly shouldn't be a problem installing the Express edition from a regular download. That's the way it's intended to be installed.

If you're using Windows XP, the only officially supported version is the 32-bit version. However, you do need to make sure that your Windows XP install is completely up-to-date and patched, with XP Service Pack 3 installed. (See http://msdn.microsoft.com/en-us/library/ms143506.aspx#Express32 for formal requirements.)

It's not unusual for the install process to take a while, and with older operating systems like XP, you'll often have to back it out and try again, as usually there's a bunch of prerequisites that need to be installed. (Like the .NET Framework 3.5 SP1, the correct version of Windows Installer, etc.)
Q: The link to the installer for the AdventureWorks sample database, as shown in the Chapter 2 movie "Installing sample databases," no longer works. Where can I find the installer?
A: Microsoft has reorganized its site. The sample files are still there, but they're a bit harder to find. To install them:

1) Visit http://msftdbprodsamples.codeplex.com/.
2) Click the link to "SQL Server 2008 R2 OLTP."
3) Click the AdventureWOkrs2008R2 Data File link and agree to the conditions to download the MDF file.
4) Move the MDF file to your SQL Server Directory, usually located at C:\Program Files\Microsfot SQL Server\MSSQL 10_50.MSSQLSERVER\MSSQL\DATA.
5) Open the SQL Sever Management Studio and connect to your instance using an account with administrative privileges.
6) Attach the sample database by right-clicking the Databases folder in the Object Explorer and choosing Attach from the pop-up menu.
7) Click the Add button in the next menu and navigate to the MDF file in the Locate Database Files window that appears. Select it and click OK.
8) Remove the reference to the log file in the "AdventureWorks2008R2" database details: pane by selecting the Log entry and clicking removing.*
9) Click OK to return to SQL Server Management Studio and complete the attachment process.

*MDF files are the "data" files for SQL Server databases. They often come along with LOG files (ldf files). This one didn't so we need to REMOVE the reference to the non-existent log file. Select the second row in the lower section (it should say File Type: Log and Message: Not Found) and click the REMOVE button.

For an illustrated version of these instructions (with screenshots), click here for a PDF version.
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