SQL Clone
SQLServerCentral is supported by Redgate
 
Log in  ::  Register  ::  Not logged in
 
 
 

#TSQL2sDay – Starting Out with PowerShell

tsql2sdayThis months TSQL2sday is hosted by me!

Surprise! – I chose PowerShell

I am really looking forward to seeing what other people post. Some advanced scripts that will help you and show you how you can use PowerShell to save you time and hopefully some beginner posts explaining experiences or showing you how to start with PowerShell and SQL Server. I decided to go with the latter.

First though a warning.

PowerShell is another language, you are not going to be as proficient in a new language as you are in the language you spend all day working with. You will have to go through the learning curve and you will have to understand how to interpret errors. There is a learning curve just like with any language. Undoubtedly you will get frustrated at times. Reach out for help. Use twitter, use the #powershellhelp in the SQL Server Community Slack channel. There are many other places and plenty of people who will be glad to help you.

Open the Editor

If you are using a Windows machine you will have PowerShell installed. You will find it in your start menu on Windows 7 under All Programs, Accessories, Windows PowerShell folder, and then click Windows PowerShell or Windows PowerShell ISE. On Windows 8 or 10 search for PowerShell.

PowerShell or PowerShell ISE? Use PowerShell instead of cmd.exe for command line usage and ISE for developing scripts, functions and modules. (However, read on before making your choice)

PowerShell on Other O/S’s (and Windows!)

Just as SQL Server is available on Linux PowerShell is also available cross-platform, you can run and edit PowerShell on Linux and on Mac natively. The best editor to use is VS Code which is also available cross-platform. In fact, as Microsofts David Wilson says in this blog post

The PowerShell ISE has been the official editor for PowerShell throughout most of the history of Windows PowerShell. Now with the advent of the cross-platform PowerShell Core, we need a new official editor that’s available across all supported OS platforms and versions. Visual Studio Code is now that editor and the majority of our effort will be focused there.

So my advice is, whichever operating system you are using, use VS Code to write, edit, debug and run your PowerShell as that is the editor where Microsoft are spending the majority of their effort in development. Follow the instructions here to install You can also use it with many other languages including T-SQL. I find it a very useful tool

Where to start?

Well that depends what you want to do. Start by reading. Start by trying to accomplish something in PowerShell even if you know how to do it another way. This will also help you to realise when you are trying to use a hammer to put in a screw (using the wrong tool for the job)

What Command?

You don’t know where to start so how do you know the command to use? Here is a first command. You will use it often. I use it everyday still despite using PowerShell daily for many years. But don’t run it yet!

Get-Command

PowerShell is quite intuitive in it’s command naming. It uses a Verb-Noun syntax. You know without me explaining what this command will do. It will “Get” the “Command” (s). PowerShell uses singular nouns for its commands. I have 8000+ commands on my machine so it would have overloaded you with commands if you had run it without filters!

We use * as a wildcard in PowerShell so we can use that with our Get-Command command to find some commands to run. Type Get-Com and then hit the tab button. This will not only help you as it will auto-complete, it will reduce the number of errors as it will only auto-complete correct command names :-).

Get-Command *service

This will show all commands which end with service. The results will have some different headings. The screenshot below shows just one command to reduce confusion.

03 - get-service.png

The type of command, the name of the command, the version of the command and the module it is in. PowerShell uses modules to group commands together and to enable you to install the ones that you require from a repository like the PowerShell Gallery (more on this later).

You can find all of the commands in a module with the Get-Command command like this

Get-Command -Module microsoft.powershell.management

This will show you all of the commands in the management module which may be a good place to start exploring. In this module for example

  • Test-Connection is like ping but better
  • Test-Path tests the existence of files and file paths
  • *-Service works with services
  • *-Process works with processes
  • *-Computer for power options for a computer
  • Get-ComputerInfo which will give you computer information (surprisingly ?? )

This is also something to remember in the future when you want to know what commands a module has or what the precise name of the command is.

Maybe once you install the dbatools module, the sqlserver module or the SSRS module??

HOMEWORK – Examine the names of commands in other modules that you find in

Get-Module

or for more choices

Get-Module -ListAvailable

How do I use that command though?

You need to read! PowerShell comes with a lot of documentation, a lot of it is available on your machine. Lets introduce another command

Get-Help

As you can imagine, this gets the help for a command or returns help topics about PowerShell. Again, I use this every single day and you should too. Lets start with the first one. Lets get help for the Get-ChildItem command

Get-Help Get-ChildItem

Now, some of you may not get very much returned and a message at the bottom which says

Get-Help cannot find the Help files for this cmdlet on this computer. It is displaying only partial help.
— To download and install Help files for the module that includes this cmdlet, use Update-Help.
— To view the Help topic for this cmdlet online, type: “Get-Help Get-ChildItem -Online” or
go to https://go.microsoft.com/fwlink/?LinkID=113308.

When you have something else to do I would recommend running Update-Help as it suggests (It can take a few minutes to run) but for now make use of the -Online switch.

HOMEWORK – Run Update-Help

Get-Help Get-ChildItem -Online

This is available for all of the Microsoft modules and some of the better open source modules, dbatools is an example of a (brilliant) community module which has -Online URLs for it’s commands. Running Get-Help (with or without the -Online switch) will give you plenty of information about the command, the switches available, the inputs and outputs.

Maybe start by using the -examples switch

Get-Help Get-ChildItem -Examples

will show you some examples of how to use the command

05 gethelp examples

Now you can start to explore the file system with this command (also the SQL Server, Registry, Certificate Store and many more things)

I also like to use the ShowWindow switch

Get-Help Get-ChildItem -ShowWindow

which will open up the help in a separate window which can be useful when you are writing a script and it is searchable

04 - gethelp showwindo

But Chrissy prefers to use the -Detailed switch

Get-Help Get-ChildItem -Detailed

You can decide which way you like best.

Now you know how to find a command and hot to find out how to use it. If you are using VS Code (or ISE) you have access to Intellisense and snippets to help you with the syntax. You can run a command and get some results.

HOMEWORK – Use Get-Help to understand how to use commands. ( Extra merit marks for teachers pets who read the topics they find using Get-Help About_*) Also, instant demerit points throughout the course (your career) for students who do not use Get-Help when using any command for the first time.

Hopefully you are confident enough to have run some commands. If you are worried about breaking things only run the commands which start with Get- as these should only be returning information or objects and not changing anything.

This isn’t cmd 

This isn’t cmd. What you are getting back is not text.

It is an object.

Unless you choose to use one of the formatting commands or the command you are using outputs using a formatting command (pro-tip don’t do that) then what you will receive as the results of your command is an object.

This means that there is more that you can do with the results than just have them in text format. You want Text File,JSON, XML, CSV, Excel output or to write to a database? Look here for ideas

Objects,Objects,Objects

Objects are awesome. Lets start with a SQL Server Instance object to show you how to explore objects. You will need to install the most useful PowerShell module you will find if you are working with SQL Server – dbatools

Disclosure – I am a contributor to the open source module dbatools. I am presenting a full day workshop in Singapore for the PowerShell Conference Asia in October. I am also proctoring at Chrissy and CK’s PASS Summit in Seattle. I highly recommend that you come and join us at one of those events if you can to further learn how you can use PowerShell to administer SQL Server

You can install it from the PowerShell Gallery using

Install-Module dbatools -Scope CurrentUser

You will be asked if you want to trust the repository, say Yes. If this doesn’t work on your machine (you are on an older version of PowerShell) follow the instructions on this page.  Or ask for help in #powershellhelp in Slack

Now that the module is installed we can create a SQL Server Instance object by assigning the results of a command to a variable.

A variable in PowerShell is designated by a $.

I suggest that you get used to following this step as well. This is a great way of exploring the results of any command and understanding what you can do with it.

We will use the Get-Member command. Another one that I use every single day.

Warning – You do not have to use these methods to accomplish tasks in PowerShell against SQL Server as both Microsoft and the community have released modules which will enable you to general tasks without “coding”

This is an example to get you comfortable with PowerShell by using a target that you are comfortable with and can recognise.

## Create a smo object provide your host\instance after -SqlInstance 
$SMO = Connect-DbaSqlServer -SqlInstance ROB-XPS\sql2016

Now that we have an object we can explore it

$SMO

By just calling the variable it will display the default properties

06 - default properties.png

If you want to see what else is available you can use Get-Member You just pipe | to Get-Member

$SMO | Get-Member

This will show you all of the events, methods and properties available on the object.  Methods are really useful, enabling you to do things like start agent jobs or enumerate permissions or members

If you wish to see all of the processes that are running on the instance

$SMO.EnumProcesses() | Out-GridView

Out-GridView is a useful command allowing you to see the results of your command in a graphical format and easily filter using the search bar at the top.

07 - ogv.png

Other things you can do include reading the errorlog

$SMO.ReadErrorLog() | Out-GridView

08 - errorlog.png

Get the connections to a database

$smo.GetActiveDBConnectionCount('master')

Get the current Traceflags

$smo.EnumActiveCurrentSessionTraceFlags() 
$smo.EnumActiveGlobalTraceFlags()

The properties that are available at this level are similar to the view that you see in SSMS Object Explorer for the instance. You can see a databases folder in SSMS and you can expand it. You can do the same in PowerShell

$SMO.Databases.Name

That is going to just show you the names of the databases on that instance. You can do the same thing using the pipe | again and Select-Object

$Smo.Databases | Select-Object Name

This will pass the Databases array of objects “along the pipeline” and then you can use Select-Object to choose them. Multiple properties can be chosen with commas.

$smo.Databases|Select-Object Name, Collation, CreateDate, Owner, version

09 - databases.png

PowerShell will let you select things that do not exist so for example

$smo.Databases | Select Name, NumberofBeards, Owner, MoustacheLength,one

does not return an error but some of the columns are empty ?? You need to use the names of the properties returned from Get-Member in your Select statement (Hmm, sounds a bit like T-SQL)

18 select.png

You can look at a single database default properties using

$SMO.Database['NAMEOFDATABASE']

You can then use Get-Member to explore deeper and deeper.

You can also look at the Agent from the instance level object

$SMO.JobServer

HOMEWORK – Using the code above explore the $SMO object, look at the databases, tables, the columns and the indexes. Explore other properties and select them. (Extra merit points for exploring the SQL Server like a file system using the SQLServer drive. Start with cd SQLSERVER:\ and use Get-ChildItem or its alias dir or ls)

Warning Reminder – You do not have to use these methods to accomplish tasks in PowerShell against SQL Server as both Microsoft and the community have released modules which will enable you to do general tasks without “coding”

But this is a very useful way of understanding and exploring using PowerShell with a type of object that you understand. You will use these methods all of the time and when you need to accomplish the next thing you have the tools. Already. Now.

Recap

You should take from this for the future

  • Get-Command *search* – Find a Command
  • Get-Help NameOfCommand – How do I use the Command ?
  • $var = Some Command here – Set the output of a command to a variable
  • $var | Get-Member – What Events, Methods, Properties do I have on this object
  • $var | Select Property1, Property2, Property3

That’s All Code – Where’s The Easy Buttons ?

There are two answers to this.

Firstly, yes it’s all code, but you will find that code is the future. Every time you run the same piece of code it will do the same thing, every time a junior DBA follows the steps to manually do something in a GUI like SSMS they may make a mistake and a different mistake each time. As DBAs we use stored procedures, views, functions and more, they are all code. Using code is vital for automation, for making things easy, for reducing the risk of mistakes, for getting rid of the mundane.

It is also required for DevopsAgileScrumContinuousIntegrationDeliveryWhatsTheNextBuzzWord which is all the rage (and also a lot of fun with interesting challenges)

As estates get bigger and bigger the GUI becomes less useful to you.

Secondly, remember my warning at the top of this post? There is no easy button. You will have to learn new things you will make mistakes and get errors, you need to ask for help

I Have An ERROR !

Don’t be disheartened, errors happen. The red text looks scary and frightening but its not.

Read the Error

Lets use Microsofts sqlserver module. There are all sorts of ways to get it. If you have SSMS you probably have it already. Lets check

Get-Module sqlserver

A result like this means that you have it

10 - get-module.png

If not

Install-Module sqlserver -Scope CurrentUser

Again you will be asked if you want to trust the repository, say yes!

If I run

Get-SqlLogin -ServerInstance rob-xps

I get

11 - error.png

That error is fairly easy to understand. I can’t connect to an instance that isn’t running

If I run

Get-SqlLogin -ServerInstance rob-xps\sql2016 -LoginName rob

I get a different error

12 sql login error.png

The Get-SqlLogin from Microsofts sqlserver module returns an error if it cannot find the specified login name. The important part of this error message is ObjectNotFound. That tells us what has happened

If we look at the logins

Get-SqlLogin -ServerInstance rob-xps\sql2016 | Select Name

13 - Logins.png

and choose one that exists everything is good

14 one login.png

HOMEWORK – Here is another object to explore with Get-Member. Explore the Login object

For example

15 - login script.png

But back to errors. Sometimes it isn’t quite so obvious. I have altered my Create-Database function so that it shows an error instead of a helpful message.

16 - db error.png

This is an example of the sort of error message that you might not be able to decipher so easily. Even if you read the message it says Exception calling .ctor with 2 arguments. How can you, as a new PowerShell user work out what has happened?

Objects

Remember, PowerShell is great because of objects? The errors are objects too. Lets have a look at the error in full. This is another piece of code that I still use every single day

$error[0] | fl -force

The $error variable holds an array of error objects for that session. The [0] targets the 1st object in the array which is the latest. We pipe that to fl which is an alias for Format-List. Normally I am very clear about not using aliases in my blog posts as I believe that you should not use aliases in your scripts and functions (This is due to a bad experience trying to google for % to find out what it was in PowerShell many years ago). However, you are only going to use this at the command line so its ok.

The results are

17 error.png

Once you read the error, you will see that there is a generic connection failed error message which you will be used to seeing and now you can go about fixing it.

Errors aren’t scary. You just have to read them. Sometimes you have to expand them to read them. Once you have read them don’t forget that there is also a lot of help out there on the internet. I recommend the #powershellhelp channel in the slack but with the full error message you will be able to get some useful results from whatever your choice of helpful solutions is.

That’s exactly 3000 words – which is slightly (!) more than I intended to write and a lot to read, so if you have got all the way down here. Congratulations, when you see me at Summit or at a SQL Saturday come up and tell me and I will give you a special sticker ??

Hopefully this has given you some guidance to starting to use PowerShell with SQL and how you can help yourself.

Good luck.

SQL DBA With A Beard

Rob is a SQL Server DBA currently supporting several hundred databases ranging from SQL 2000 to SQL 2012. Rob has a fabulous beard and loves to use Powershell to make his life easier.

Comments

Leave a comment on the original post [sqldbawithabeard.com, opens in a new window]

Loading comments...