Tag Archives: powershell

A Condemnation of Invoke-SqlCmd

Recently Mike Fal penned a post defending the Invoke-SqlCmd cmdlet. This is a response to that post. (Update: Apparently Mike Fal’s post was in response to a post by Drew Furgiuele that was also critical of Invoke-Sqlcmd.) I want to give Mike proper credit: he states multiple times that Invoke-SqlCmd is not the right tool for every sql-related job. Kudos for that. However in this post I’m going to make the argument that Invoke-SqlCmd is the wrong tool for any job, period.

I believe that not only is Invoke-SqlCmd deficient, but is also potentially dangerous to use in production. Let me immediately clarify: I’m not saying the cmdlet is buggy. I’m simply saying that the way it’s intended to be used encourages bad coding practices that, at the very least can produce unintended results, and at worst can introduce serious security issues.

The root cause of all the issues with Invoke-SqlCmd cmdlet is that it’s the classic sqlcmd.exe utility that has some powershell hammered onto it. As a result, most of the patterns and conventions used for cmdlets are thrown out the window in order to maintain backwards compatibility with the base executable. Here’s a great example:

PS c:\> Invoke-SqlCmd -ServerInstance "MyServer\MyInstance" -Database "db1" -Username "ctigeek" -Password "whyAmIPassingInAPassword???" -Query "select * from sometable1"

Now I challenge you to find one other cmdlet, published by Microsoft, that accepts a clear-text password on the command line. Any other cmdlet that needs this information takes in a Credential object. Another example is how it uses the AbortOnError switch instead of the standard ErrorAction parameter. All of these proprietary parameters are intended to maintain parity with the underlying executable. The MSDN documentation even itemizes which options from sqlcmd.exe are included and how they map to the powershell cmdlet. I find all this completely intolerable. The standards by which Powershell commands are built should not be bent (or in this case, flat-out broken) in order to conform to the underlying executable. If DBAs want to use sqlcmd.exe, then they can use it directly without this layer of obfuscation that doesn’t appear to add any real value.

Sqlcmd.exe was originally designed for DBAs to execute DDL and other scripts related to the administration of the database. Yes, it can also return data; it was built to generate “flat” static-font reports that you see printed out in any 80s TV show that had a computer in it. This is how most db reports were generated up until relatively recently. My point is this: sqlcmd was never intended to be used to query data in the kind of environment in which it is used with Powershell. In other words, it is completely lacking in the features necessary to be a useful and safe tool in a modern production application.

  1. It doesn’t support ANY standard cmdlet parameters. I would expect any cmdlet published by Microsoft, especially one that interacts with a database, to have ErrorAction, Verbose, WhatIf, and Confirm. If it can consume user IDs and/or passwords, I expect it to accept a Credential object.
  2. It doesn’t support non-queries or scalar queries. If I execute an update or delete using Invoke-SqlCmd, I will have no idea how many rows I just impacted. If confirmation is a requirement, I then have to execute a second, possibly expensive table-scanning, query to confirm.
  3. It doesn’t support transactions. I can’t overemphasize how big a deal this is. This is one of those things that people don’t think about because it’s not even available. The only way to do transactions with Invoke-SqlCmd is by having the entire transaction inside the SQL command being sent. This usually isn’t practical, sometimes necessitating the script to dynamically generate the sql with all the correct commits, rollbacks, and checks thereto. That’s insane. And it completely prevents the Powershell script from doing other things within the scope of the transaction. Did you know that Powershell supports distributed transactions? Yup. You can start a transaction, make changes on multiple database servers, change a file, a registry key, and put a message into an MSMQ queue, all part of a transaction. But Invoke-SqlCmd doesn’t support that.
  4. Support for SQL parameters is awful. This is the dangerous part I was eluding to earlier. The support for defining and passing in parameters is awful. How bad? The variable and the value are defined in a single string. e.g. "var1='val1'" And you have to escape single quotes in the value. This means that if the values are already in proper Powershell variables, you have to escape the value, build strings, put that into an array, pass that into …. never mind. It’s an unusable mess. And that’s the point. Anyone with 5 minutes experience with Powershell will just create the SQL using string concatenation based on the function’s input parameters. And of course that’s begging for a whole litany of security issues. If proper SQL parameters were supported, people would use it.
  5. It only supports Sql Server. Do you really only EVER work with Sql Server? Ever? If so, good for you, but in 20 years that’s never been the case for me. The great thing about SQL is that it’s (mostly) universal. I want a Powershell command that works the same way, with the same options, across any relational database.

So what’s the harm if Invoke-SqlCmd supports your current needs? The problem is your needs tomorrow will be different. Your code is going to change, and sooner or later you’re going to hit the much-closer-than-you-think wall of usefulness. So what’s the alternative? Lots of .NET coding?

Two years ago I realized all this and started the OSS project, InvokeQueryPowershellModule. It’s written in c#, based on ADO.NET, and supports all of the functionality above and more. There’s lots of examples in the Readme. It’s available from the Powershell gallery now. I’ve been using it in a production environment for over a year with no issues. I strongly encourage you to consider it as a superior alternative.