I usually avoid nullable columns, but sometimes date fields make sense to be null (rather than use sentinel values like 1/1/1900).  In this case, I had a nullable date column and I needed to check in PowerShell whether the field was in fact null or not.  In SQL, I would have just used an IS NULL, or used the IsNull() function to replace the null value with something a little easier to deal with.  My first (feeble) attempt was to do this:

if (!$_.completedDate){
# it’s null
}

Unfortunately for me, that doesn’t work.  Next, I used this (which worked, but wasn’t very satisfactory either):

if ($_.completedDate.ToString() -eq ''){
# it’s null
}

Realizing that I was being stupid, I googled “PowerShell SQL NULL and after looking at several pages which didn’t really address the issue, I found this. A little work to change it into a function, and voilà.

function is-null($value){
  return  [System.DBNull]::Value.Equals($value)
}

A few quick tests and this is what I wanted. Now, my code looks like this:

if (is-null $_.completedDate){
# it’s null
}

I find it hard to believe I haven’t written this function before (or seen it).

By the way…be watching the SQL PowerShell Extensions project.  Chad released version 2.1, which includes SQL mode for the ISE (really nice).  I know he and several others are collaborating on an update which should be out sometime soon.

-Mike

Chad Miller, the driving force behind SQLPSX, has put a lot of effort into this release, and you’ll find really good examples of advanced functions (with comment-based help, even).

If you deal with SQL Server in any way, you’ll almost certainly be able to use this set of modules to streamline your scripting experience (and probably learn something about SMO in the process).

You can find the release here.