Table Column Differences with T-SQL and PowerShell – Part 2

If this was a horror movie, it would be called “The Differencing”…duh duh duh!

The original post for this topic garnered the attention of a commenter who pointed out that the same result could be gathered using a couple of UNION ALLs and those lovely set-based EXCEPT and INTERSECT keywords.

I personally think that both options work and whatever you feel comfortable with, use that.

It did play on my mind though of what the performance differences would be…what would the difference in STATISTICS IO, TIME be? What would the difference in Execution Plans be? Would there even be any difference between the two or are they the same thing? How come it’s always the things I tell myself not to forget that I end up forgetting?

I have no idea about the last one but at least the other things we can check. I did mention to the commentor that I would find this an interesting blog topic if they wanted to give it a go and get back to me. All I can say is – Sorry, your mail must have got lost in transit. I’m sure it is a better blog post that mine anyway.

If you’re going to do it…

For this test, we’re not going to stop at a measely 4 columns per table. Oh no! For this one we’re going to go as wide as we can.

With a recent post by Kenneth Fisher ( blog | twitter ) out about T-SQL FizzBuzz, I’m going to create two tables, both of which will have incrementing column names i.e. col00001, col00002, …, col1024. Table1 will have all columns divisible by 3 removed while Table2 will have all columns divisible by 5 removed.

See, FizzBuzz can be useful!

So our table creation scripts…

SELECT TOP (1024)
    CASE WHEN v.number = 0
      -- Change this to 02 the second run through
THEN N'CREATE TABLE dbo.TableColumnDifference01 ('
    ELSE N' col' + RIGHT(REPLICATE('0', 8) + CAST(v.number AS nvarchar(5)), 4) + N' int,'
    END
FROM master.dbo.spt_values AS v
WHERE v.type = N'P'
AND (
-- Change this to '% 5' the second run through
v.number % 3 != 0
OR v.number = 0)
FOR XML PATH('')
TableCreationScript
See Note

NOTE: When you copy and paste the results of this query into a new window to open it, it is going to fail. Why? Well the end of the script is going to be along the lines of colN int, and it needs to be colN int). Why is it like this? Well it was taking to damn long to script that out. Feel free to change this to work for you. Hey if you do, let me know!

Now, how I’m going to do test this, is run each method 3 times (PIVOT, UNION, and PowerShell), then measure the third run of each method. This is mainly as I want to get rid of any “cold cache” issues with SQL Server where the plan has to be compiled or the data brought into memory.

…do it Pivot

So first up is the Pivot method from the last blog post. In case you’re playing along at home (and go on, do! Why should kids get all the fun) here is the code that I’m running.

And here is our results:

PivotMethodGridResults
Yup, those be columns

What we are really after though is the stats, execution plan and time to complete for our 3rd execution. Now as much as I love reading the messages tab for the stats information, I feel with blog posts that aesthetics is king, so I’m going to be using the free tool by Richie Rump ( twitter ) “Statistics Parser

Stats:

PivotMethodGridStats
Elapsed time: 00:00:00.136

 

Execution Plan:

PivotMethodGridPlan
Probably the first plan I’ve seen where the SORT isn’t the most expensive!

..do it UNION

Secondly we have what I dubbed “the UNION method” (no points for figuring out why) and the only change I’ve made to this script is to add in PARSENAME() and that’s only so that the script would..you know…work.

Results be like:

UnionMethodGridResults
Yep, Yep, Yep, Yep, Nope, Yep…

Stats:

UnionMethodGridStats
Elapsed time: 00:00:00.624

hmm…less Scan Counts but 5 times the reads…also 5 times slower than the PIVOT method. Maybe the execution plan will be prettier?

Execution Plan:

UnionMethodGridPlan.png
ehh…WHAT!

Yeah…so…that’s…that’s different from the first plan! I was right in my comment though, there is a concatenation operator (there’s actually 2, you may need to zoom in to find them though)

…do it PowerShell

Finally we have the PowerShell method. No messing about here, let’s get straight to it! I’m going to lump all the code together in one gist and I’ll be wrapping it in Measure-Command to get the speed of the command.

Get-Results

PoSHMethodGridResults
Yeah I’m liking VS Code more and more…

Get-Stats:

PoSHMethodGridStats.png
Elapsed time: 00:00:00.249

help *execution*; help *plan*

Would you believe that I couldn’t figure out how to get an execution plan for PowerShell 🙂

If anybody knows, hit me up!

Finishing off

You know at the start of this, I was fully expecting the PowerShell to win out, followed by the UNION method, because it’s use of UNION, EXCEPT, and INTERSECT which are basically made for this kind of problem, and the PIVOT method bringing up a distant last since PIVOTs have this complexity stigma attached to them and what is complex is normally slow.

From a sheer speed point of view, the actual results are:

  1. Pivot
  2. PowerShell
  3. Union

Who knew!?

I don’t think this is the end of my use of PowerShell or Union operators though. I’m not going to replace all the stuff that I can with Pivots. For one I just think that PowerShell and the Union operators are just too cool!

I actually like this result for two reasons.

  1. There are multiple way to do something in SQL, there are good ways and better ways. The main point is whatever option you choose, make sure you know what it entails and can justify it.
    Whatever works for you, works for you!
  2. You don’t know something, test it and find out! What you think the outcome may be, may not be true.

Now if you’ll excuse me, I want to figure out if there’s a way to return execution plans with PowerShell.

 

Chaos Theory, Compound Effects, and Consequences.

Straight away I want to apologise for the Nicolas Cage memes!

User Groups are great, aren’t they?

I just got back from the Reading User Group and I’m still in that post “User Group Glow”, also known as “Long Day Lethargy”, or “Twelve Hour Tiredness”.

They are great though! A chance to talk to other people in the SQL Server community, – a slight reminder that even if you work alone, people are still experiencing some of the same problems that you are (apparently everyone has to deal with multiple nested views, who knew!) – a chance to hear presentations on different topics, and pizza if you’re lucky (we were).

WishYouWereHere.PNG
They’re really great!

I realised during the session that the two presentations given during the User Group had a connection with a small issue with a table change I had been given with a developer.

Here’s what did not happen to me so you can watch out for it.

The Chaos Theory

NicCageChaos.PNG
Nic Chaos

 

Raul Gonzalez ( blog | twitter ) was first up with this presentation “Database Design Matters, Seriously”, showing us the chaos that can occur from not giving some serious thought into how you design your database.

His session is not yet up on his blog as I’m writing this but it will be soon so keep an eye out for that!

Now he had a lot of good points but, for brevity’s sake, the main chaos theory points here are what happens if you don’t take advantage of CHECK CONSTRAINTS, FOREIGN KEY CONSTRAINTS, and not specifying a columns NULLABILITY (yes, that’s a word!). SQL Server is a powerful program with many performance optimizations provided for you, but it’s not omniscient; it can only use the information that you give it!

His points on NULLABILITY (I mean, I think it’s a word) tied in nicely with the next presentation…

Compound Effects

NicCageChaos.PNG
Compound Effects

David Morrison ( blog | twitter ) followed up with his presentation on “Query Plan Deep Dives” (I had seen this at SQL Bits, but it’s a great session so I had no problems watching it again) and, as an aside, through his presentation he showed us the compound effects that can happen from not specifying a columns NULLABILITY (it’s got letters so it’s word-like…)

Now his slides and scripts are up on his blog and they do a great job of walking you through them so check them out and you’ll see the compound effects they create!

Here’s a little teaser…


-- now I want all people who's email isn't in the email table
SELECT /*C.FirstName ,
    C.LastName ,*/
    C.EmailAddress
FROM dbo.Contact AS C
WHERE C.EmailAddress NOT IN (SELECT E.EmailAddress
                             FROM dbo.Emails AS E)

GO
NULLABILITY.png
This should be A LOT simpler!!!

Consequences

Which brings us back around to consequences or as I like to put it “How I Pissed Off A Dev By Refusing A Simple Request”.

To be quite honest, it was a simple request. A requirement came in to expand a column datatype up to varchar(100), so one of devs wrote up a simple script and passed it onto the DBAs to check as part of the change control procedure.

ALTER TABLE tablename
ALTER COLUMN columnname varchar(100)

And I said no.

WHY???!!!“, you may shout at me (he certainly did), but I’m going to say to you what I said to him. “Give me a chance to explain before you take my head off, alright?”

ArgumentInvalid.PNG
Argue with a DBA, go on!

While there is nothing wrong with the above code syntactically (is that a word?) but I couldn’t approve it since that column was originally NOT NULL and the above script would have stripped the column of that attribute! Business requirements dictated that it should not allow NULLS, and hey, who are we to argue with that 😐

Double checking to see if the column is NULL or NOT NULL allowed me to see a problem with that code, one that many people would consider simple enough to just allow it through at a quick glance. Which could have opened up problems further down the line if it had run…

Thanks to the User Group, I now know that it could have a knock on effect with our query plans as well!

ALTER TABLE tablename
ALTER COLUMN columnname varchar(100) NOT NULL

There, that’s better!

DBAs deal with databases and consequences

YDS.PNG

 

DBAs get a lot of stick sometime, the “Default Blame Acceptors” or the “Don’t Bother Asking” but a lot of the time, it’s not that we want to say no, it’s just that we have to take into consideration a thousand little things that could snowball into 1 giant problem.

With the rise of DevOps, check out the latest T-SQL Tuesday, DBAs have gone from going

“No”

to somewhere along the lines of

“Not this second, let me check it out and see what we can do”

If pressed further, we may rely on the good, old “it depends” though. Hey, clichés are there for a reason; they work!

It just goes to show that, like the IT profession, DBAs are constantly evolving.
Continuosly learning, checking out new helping technologies, and going to User Groups are going to help us to deal with it.

Just remember, in the end,

LeFin.PNG

P.S. I should probably mention that the Nicolas Cage memes are because of this blog post by Nate Johnson ( blog ) that I enjoyed so much that I had to do something in response. I’m not normally this crazy, I swear!

Problems Creating XML Schema Collection

Ever created an XML Schema collection before? Our developers work with a lot of XML so I wasn’t surprised when eventually a request came in about permissions with XML SCHEMA COLLECTION.

Surprised that they had a permissions issue, yes, but not surprised that they were working with XML.

Why is it “an XML” and not “a XML”?

For information purposes, I’d normally provide a brief description of what an XML SCHEMA COLLECTION is but, being completely honest, I’m still not sure I can vocalize it in an understandable way. It’s kind of like explaining the colour purple without using other colours (and yes, that’s colour with a ‘u’).

I know what it is, I just can’t explain it properly…yet

So what I’m going to do is point you to the link for Microsoft docs for XML Schema Collection (done) and just gloss right over it (nothing to see here).

Permissions Shane, you mentioned permissions.

Right, sorry.

Investigation first. This was on the Development server and they had emailed me the creation code along with the error message they had received, which was this guy:

CREATE XML SCHEMA COLLECTION name AS
N'RANDOM XML ALERT...'

Msg 2797, Level 16, State 2, Line 20
The default schema does not exist.

However, when I ran the code, I got a different error message, mainly this guy:

CREATE XML SCHEMA COLLECTION name AS
N'RANDOM XML ALERT...'

Msg 9459, Level 16, State 1, Line 3
XML parsing: line 2, character 34, undeclared prefix

Which meant I had to go back and tell them to fix their darn XML.

Now I’m pretty sure we have a problems though:

That error message did not fill me with confidence. Yeah, sure they had bad XML but I was now fairly sure that there was also a permissions problem. Mainly because if there’s one thing that I’ve learned so far, it’s this:

No good can come from two different people getting two different errors from the same code!

Proper XML:

Proper XML was provided and ran by the developers but the same error message came back…

CREATE XML SCHEMA COLLECTION name AS
N'random xml alert...'

Msg 2797, Level 16, State 2, Line 20
The default schema does not exist.

The difference this time was, when I ran the code, I received the following message

Command(s) completed successfully.

…That’s not good.

Developers happy. DBAs not.

At this stage, I’m nearly convinced that it’s a permissions issue.

Checking the permissions required to create an XML Schema Collection doesn’t help, since the Devs were part of the db_dlladmin database role, so that should have been covered.

In my head I’m thinking of all the things that I can do to try and troubleshoot this problem.

  1. Extended Events my session,
  2. Ask my Senior DBA,
  3. Cry

Then I realize that I’m jumping the gun again and I slow down, and check the first error message again. This time without the developers shouting in my ear, about permissions.

The DEFAULT schema

That says “schema”, not “permission”. Maybe the difference between the DBAs and the Devs was to do with default schema and not permissions this time. Let’s check it out!

SELECT
    IIF(principal_id = 1, 'DBA', 'Dev') AS DBPrincipal,
    default_schema_name
FROM sys.database_principals
WHERE principal_id IN (1, 14);
DiffSchema
Devs don’t even have a default schema!

Wait, so it was a SCHEMA issue?

Have you checked the Examples section of Microsoft Docs? Normally, they are a great source of material for examples but if you check out the examples for XML Schema Collection , not one of them shows the schema name in the examples.

So, I walk over to the original developer and his machine, change his code to…

 
CREATE XML SCHEMA COLLECTION dbo.name_test AS 
N'RANDOM XML ALERT...' 

And it works!

Apparently what had happened was the Senior Dev had gotten sick of developers not specifying the schema when creating objects and had asked the Senior DBA to remove the default schema for Developers. That seems to work (by that I mean, everything error-ed out correctly), they were happy that developers now had to specify the schema, and life moved on.

Yet, later on, when the developer read the docs for XML Schema Collection, and saw that there was no schema in the examples, it didn’t cross their mind that a schema was required. So they didn’t specify it and that, in combination with no default schema, caused this whole mess.

The (fast food) takeaways:

  1. Slow down! Don’t jump the gun,
  2. Developers don’t know everything,
  3. It’s not always permissions,
  4. Schemas are important(!),
  5. Having checklists for investigations are highly useful, and
  6. Documentation, especially on past decisions, are even more useful!

Apologies for the blurb of a blog post but I have to go.
Apparently, there’s a permissions issue with a Stored Procedure now…

 

 

Why I *try* to help with dbatools?

Can I get a couple more hours in each day please?

This post started after I created a function for dbatools, was resurrected when talking to Chrissy LeMaire ( blog | twitter ) then died down again afterwards. At this stage, I figure I publish it now or I’ll never finish it.


2 fricking hours…

I’m a Junior DBA, and as one, I get given the graft work.

For me that meant manually checking the backups. Every single file of every single database of every single server, every single day…plus whatever other jobs and alerts had come in overnight.

As you can imagine, it took a while (OVER 2 HOURS!!!) and since my youth, I had leveled-up from ‘laziness’ to ‘efficiency’, so I wanted a better option.

I had heard about PowerShell as a language before and wanted to check out if it was possible to use it to help me out.

So I opened up my PowerShell ISE, rested my fingers on the keyboard and…nothing.

So I checked out solutions online, and it was there that I found dbatools.io!

They had everything – or what I thought was everything since they have an issues page in github with over 100 items – so one Friday night I downloaded their tools at home and started getting familiar with them. (I know, rock star lifestyle that I have).

Monday morning, bright-eyed, bushy-tailed and filled with coffee, I sit down at my computer, open up PowerShell to start my graft work, and in 2 minutes I was finished.

2 fricking minutes…

With that, I was hooked; Twitter account, followed, Slack channel, signed in, anything and everything I could do to learn more about this wonderful life-saving (I figure time is life ergo this was life-saving) tool I was in!

But it wasn’t enough… they had given to me and I had no method to repay them.

Then one day, I asked a question on PowerShell help and one of their members Constantine Kokkinos ( blog | twitter ) helped me, and we got chatting.

He gave me an enhancement request to look at and I spent 3 days looking, poking and prodding it until finally I gave up and did a replace to fix it.

I then proceeded to try and push my entire computer into their Git repository but CK laughed and help me fix that too.

Then, from nowhere from my point of view, Chrissy LeMaire said she like it and, like that, it was in!

I’ve done more stuff since then, one more enhancement that wasn’t accepted (no worries) and a command that was accepted (that I am ashamed about since I think it’s not good enough), but I am constantly thankful for the work that they do and the knowledge that they impart.

2 commits later…

I know, I know, here I am trying to wax lyrical about dbatools when I’ve only done 2 commits.

What can I say, I’ve slowly gotten busier and busier to the point that I’m trying to schedule my days to fit everything in (if you had told me earlier that I would become a “not enough hours in the day” guy…).

Does this mean that my love for dbatools has weaned? Not in the slightest! I’m still impressed every single time that I look in (seeing as that is every day, I’m spending a lot of my time being impressed) and I’m still trying to get back to it.

2 things left to say…

  1. To anyone hesitant about getting started with dbatools, whether that is helping out or using them, I urge you not to be.
    They are welcoming, warm, and inviting people who are happy to receive help from anyone willing to give it.
  2. I’ll eventually get around to fixing that issue Chrissy, I swear 😦

Keeping New Lines in SQL Server.

Where I compare scripts to BBQ because of course I would 😐

I have this personal opinion that one sign of a good DBA is their ability to automate things and, before the DBA world found PowerShell, the way to do this was with T-SQL.

For example, a T-SQL script to get permissions assigned to a database principal could also include a column to REVOKE those permissions. This could be “automated” with some dynamic SQL.

SELECT dprin.name AS DatabasePrincipalName,
       OBJECT_NAME(dperm.major_id) AS ObjectName,
       dperm.permission_name AS PermissionName,
       N'REVOKE '
         + dperm.permission_name
         + N' ON OBJECT::'
         + OBJECT_NAME(dperm.major_id)
         + N' FROM '
         + dprin.name COLLATE Latin1_General_CI_AS AS RevokeMe
FROM sys.database_permissions AS dperm
INNER JOIN sys.database_principals AS dprin
  ON dperm.grantee_principal_id = dprin.principal_id
WHERE dprin.name = 'public';
RevokePermissions
This can be improved A WHOLE LOT…

What about if we want to improve this?

This is nice but what about if we are paranoid forward-thinking enough to realize that this could cause us problems?

“How?” You ask. Well what happens if there existed another database, say [NeedsAllPermissions], with the same table name and the same login has permissions on it.

Are you going to revoke permissions from that database? It needs ALL of them! It says so in the name!

So in an effort to not shoot ourselves in the foot, we add in the database name to our revoke script.

SELECT dprin.name AS DatabasePrincipalName,
       OBJECT_NAME(dperm.major_id) AS ObjectName,
       dperm.permission_name AS PermissionName,
       N'USE '
         + DB_NAME()
         + 'GO'
         + N'REVOKE '
         + dperm.permission_name
         + N' ON OBJECT::'
         + OBJECT_NAME(dperm.major_id)
         + N' FROM '
         + dprin.name COLLATE Latin1_General_CI_AS AS RevokeMe
FROM sys.database_permissions AS dperm
INNER JOIN sys.database_principals AS dprin
  ON dperm.grantee_principal_id = dprin.principal_id
WHERE dprin.name = 'public';

WithDBNoChar10

Yes, we’re only using our database now!

So all is well with the world…

Until the day comes when you actually want to revoke permissions to that user. So you run the above code, copy the RevokeMe column and paste it into the management window. and you get…

NoNewLine
No GO my friend…

GO is a special little guy. It’s not exactly T-SQL. It’s a way of telling the SQL Server Management Studio (SSMS) to send everything before it, from the beginning of the script or the preceding GO, to the SQL Server instance.

If you read the documents, the main point to take away is…

A Transact-SQL statement cannot occupy the same line as a GO command. However, the line can contain comments.

GO is a special little snowflake and needs to be on his own line then. Simple enough if you know that SQL Server converts CHAR(10) into a New Line.

If you didn’t know that, well you know that now….P.S. CHAR(13) is a carriage return 😉

So let’s update our script with some CHAR(10) and see what happens then.

SQL & BBQ, both work well with CHAR

SELECT dprin.name AS DatabasePrincipalName,
       OBJECT_NAME(dperm.major_id) AS ObjectName,
       dperm.permission_name AS PermissionName,
       N'USE '
         + DB_NAME()
         + CHAR(10)
         + 'GO'
         + CHAR(10)
         + N'REVOKE '
         + dperm.permission_name
         + N' ON OBJECT::'
         + OBJECT_NAME(dperm.major_id)
         + N' FROM '
         + dprin.name COLLATE Latin1_General_CI_AS AS RevokeMe
FROM sys.database_permissions AS dperm
INNER JOIN sys.database_principals AS dprin
  ON dperm.grantee_principal_id = dprin.principal_id
WHERE dprin.name = 'public';

 

WithDBAndChar10
That smokey, wood-fire CHAR

Now, when we paste the RevokeMe column to a new window, we get…

StillNoNewLine
Oh look, it’s a wild, rare nothing…I love them!

…absolutely no difference. 🙂

Why am I smiling?

Here, around 500 words in, we get to the meat of our post. How do we keep new lines when copying in SQL Server?

Tools | Options | Query Results | Results to Grid | Retain CR/LF on copy or save

Two things need to be done here.

  1. This checkbox needs to be enabled.

    KeepNewLines
    CHECK!
  2. A new window needs to be opened and used.

New window open, we run our script again, and this time, when we copy and paste the results, we get…

FinallyWorks
Winner, Winner, BBQ Chicken Dinner

Dessert:

So if you are using T-SQL to create scripts, and you’re having this problem with GO or just new lines in general, make sure that the “retain CR/LF on copy and save” checkbox is ticked.

Now, improve that script more, throw it in a stored procedure, and you never know, it may be semi-useful. 🙂

Why You May Need More Than FOR XML PATH(”)

XML – both easy, easy, lemon easy and difficult, difficult, lemon difficult…

Working on a blog post and I came up against a problem that I had heard of before but did not spend much brain-CPU power against.

know I’m going to run into this again so let’s document this for future me. Oh he’s going to appreciate this so much!

Commas are all the rage nowadays:

There are a fair number of questions nowadays about returning data from a database in a comma separated string. Sure the application should probably do that but hey, database servers are expensive, why not get some bang for your bucks!

Done!-ish…

SQL Server 2017 has this lovely function called STRING_AGG()

Pop in your column and your separator and it takes care of it for you!

…wait not everyone has SQL Server 2017 yet?

…wait don’t have SQL Server 2017 yet? Oh, I should really fix that…

Pre-SQL Server 2017:

So what can we do if we are not on SQL Server 2017? Take the advice that I was given for most of my life and STUFF it!

The STUFFing:

Our playground:

USE tempdb;

-- Test table
SELECT dt.comments
FROM ( VALUES ( 'XML is the bomb!'),
              ( '& JSON is cool too...')
     ) AS dt (comments);
TestTable
testing stuff…

 

Plain Old STUFFing:

I’m not the biggest fan of stuffing if I’m honest…tastes like dirt to me but hey, it works in 99% of situations…

SELECT STUFF((SELECT ', ' + dt.comments
              FROM ( VALUES ( 'XML is the bomb!'),
                            ( '& JSON is cool too...')
                   ) AS dt (comments)
              FOR XML PATH('')
             ), 1, 1, '') AS CommentsEnXML;

 

StandardWay
…that’s…that’s not what I said!

Bacon Sausage STUFFing however:

So…SQL Server is trying to be too helpful. What do we do? I normally turn to the SQL community and people like Rob Farley ( blog | twitter ), who has a lovely post about this.

So let’s try it out.

SELECT STUFF((SELECT ', ' + dt.comments
              FROM ( VALUES ( 'XML is the bomb!'),
                            ( '& JSON is cool too...')
                   ) AS dt (comments)
              FOR XML PATH(''),
              TYPE).value('.', 'varchar(max)'
             ), 1, 1, '') AS CommentsEnXML;

 

BetterWay
That exclamation mark is annoying me 😡

I just eat the turkey around the STUFFing:

Little hiccup in preparing for my next post. Thankfully I learn from my mistakes and failures (there’d be no help for me otherwise!).

I’ll leave this post with a quote from the blog of the main man himself:

It’s a habit I need to use more often.

Yeah, me too Rob, me too…

My Function Won’t Accept Parameters? Get-Help!

Getting Get-Help Help

The following is a recounting of an issue that I had and how I went about resolving it. No computers were harmed in the making of this post.


Ask me for one PowerShell command that everyone should know and I can answer you: Get-Help.

Fairly descriptive name if you ask me. Today I’m focusing on using Get-Help selectively to help me figure out why my custom function just won’t accept parameters!

You say Test Case. I say Basket Case.

We are going to need a custom test function for the audience to play along with at home, luckily Shane’s got you covered.
This is a Tactical Estimation of Shane’s Test function – aka T.E.S.T. function; very simple but all the important parts are there.

Function Test-FunctionByParameter {
    [cmdletbinding()]
    Param(
        [Parameter(Mandatory = $true,
                   ValueFromPipelineByPropertyName = $true)]
        [string]$Parameter
    )
    process {
        "Success, I'm [$Parameter]"
    }
}

If I’ve done my maths right, and I always do my maths right (as far as you know), then this function should take input from the pipeline and output it in the string “Success, I’m …”

Do I do my maths right?

Get-Service -Name *sql* |
Select Name -first 1 |
Test-FunctionByParameter
FirstFailure
It’s the “carrying the 1” that always gets me!

Huh, parameter problem.

I thought this was supposed to work like this. You pipe in information, magic happens, and functions work, no?

Well, when in doubt, Get-Help.

Get-Help:

Before I go any further though, just so that everyone knows how to use Get-Help, I’m going to show you one of the secret techniques for using Get-Help.

Get-Help *help*
GetHelp_Help

Yup, I use dbatools

Why does help exist?

When you think about it, why is there even a function called help?
As far as I’m aware it’s basically the same as Get-Help except it automatically pipes the output to | more so we get pages rather than a wall of text.

Is there more that we can do with Get-Help though? Is there a way that we can return the examples only? Syntax only? Parameters only?

Is there not a way that we can do such things?!

Yessum, the Possums cousin

Okay I cheated on the first one; examples are pretty easy. PowerShell actually already takes care of that for you.

Get-Help Get-Help -examples
GetHelp_GetHelp_Examples
Help me if you can I’m feeling examples…I mean down!

The other two, while not laid out for you as pretty as that, are not that difficult to do. What needs to be remembered about Get-Help is that it is a cmdlet. And what do cmdlets normally output?…

What?! No! Objects!
They normally output Objects! Wow…next time just pipe it to Get-Member if you don’t know.

I Object!

Now I first saw this done in a blog post by Adam Bertram ( blog | twitter ) but I do believe that it warrants further highlighting.

If you did pipe Get-Help to | Get-Member you would have seen a NoteProperty called syntax, so if we want the syntax for a cmdlet, we can specify that using:

(Get-Help Get-Help).syntax
GetHelp_GetHelp_Syntax.PNG
Syntax, useful for all languages

So for parameters we need…yup .parameters.

(Get-Help Get-Help).parameters
GetHelp_GetHelp_Parameters
Parameters…languages use them as well I guess

Hmm, not as handy as I thought it would be. What happens if we pipe that to Get-Member (Alias gm as I’m getting lazy here)?

(Get-Help Get-Help).parameters | gm
GetHelp_GetHelp_Parameters_GM.PNG
Well lookie here, another NoteProperty!

Let’s try that and see what we get, shall we?

(Get-Help Get-Help).parameters.parameter
GetHelp_GetHelp_Parameters
…the exact same 😡 Fine, have the same screenshot then!

It’s always brightest before the dawn

And the answer comes always before you smash your screen in rage.

If we pipe the above information to Get-Member again, we get more useful information this time (I’m not going to show it, you know how to pipe to gm by now).

GetHelp_GetHelp_Parameters_GM_Useful
This looks like something we can work with 🙂

I’m from a database background so can we make this pretty, all I care about is the name and the pipeline input.

(Get-Help Get-Help).parameters.parameter |
    Select-Object -Property name,pipelineinput
GetHelp_NamePipelineInput.PNG
ByPropertyName…what’s that?

By Odin’s Beard! I mean PropertyName

You know one of these days I should really read this help file (you should too) because half way down the results of the following code is some interesting info…

help about_pipelines

METHODS OF ACCEPTING PIPELINE INPUT

Cmdlets parameters can accept pipeline input in one of two different ways:

— ByValue: Parameters that accept input “by value” can accept piped objects
that have the same .NET type as their parameter value or objects that can be
converted to that type.

For example, the Name parameter of Start-Service accepts pipeline input
by value. It can accept string objects or objects that can be converted to
strings.

— ByPropertyName: Parameters that accept input “by property name” can accept piped
objects only when a property of the object has the same name as the parameter.

For example, the Name parameter of Start-Service can accept objects that have
a Name property.

(To list the properties of an object, pipe it to Get-Member.)

Some parameters can accept objects by value or by property name. These parameters are
designed to take input from the pipeline easily.

So that’s the problem?! The names need to match up! I can do that with Select-Object!

All I need to do is add a custom label using @{Label='<custom label>';Expression={'<custom expression>'}}

Try{}Catch{}Finally{}

Get-Service -Name *sql* |
Select-Object -First 1 -Property @{l='Parameter';e={$_.Name}} |
Test-FunctionByParameter
ParameterName_TestFunction
I always do my maths right!

So now when I run a command and get the crazy…

The input object cannot be bound to any parameters for the command either because the command does not take pipeline input or the input and its properties do not match any of the parameters that take pipeline input.

I can just run:

(Get-Help <cmdlet name>).parameters.parameter |
Select-Object Name,pipelineInput

And know exactly where to fix! 🙂