Returning a Row Count for a DataRow in PowerShell

问题

My script is populating a datarow from a stored procedure in SQL Server. I then reference specific columns in this datarow throughout the script. What I'm trying to do is add functionality that takes action X if the row count = 0, action Y if the row count = 1, and action Z if the row count > 1.

-- PowerShell script snippet

# $MyResult is populated earlier; 
# GetType() returns Name=DataRow, BaseType=System.Object

# this works
ForEach ($MyRow In $MyResult) {

    $MyFile = Get-Content $MyRow.FileName
    # do other cool stuff
}

# this is what I'm trying to do, but doesn't work
If ($MyResult.Count -eq 0) {
    # do something
}
ElseIf ($MyResult.Count -eq 1) {
    # do something else
}
Else {
    # do this instead
}

I can get $MyResult.Count to work if I'm using an array, but then I can't reference $MyRow.FileName directly.

This is probably pretty simple, but I'm new to PowerShell and object-oriented languages. I've tried searching this site, The Scripting Guy's blog, and Google, but I haven't been able to find anything that shows me how to do this.

Any help is much appreciated.

回答1:

It has everything to do with how you populate $MyResult. If you query the database like

$MyResult = @( << code that returns results from database >> )

that is, enclosing the code that returns your dataset/datatable from the database within @( ... ), then number of rows returned will be easily checked using $MyResult.count.

Your original code should work as-is if you populate $MyResult this way.

回答2:

I don't have experience with PS and SQL, but I'll try to provide an answer for you. If you're object $myresult is a datarow-object, it means you only got the one row. If the results are empty, then $myresult will usually be null.

If you get one or more rows, you can put them in an array and count it. However, if your $myresult are null, and you put it in an array it will still count as one, so we need to watch out for that. Try this:

If ($MyResult -eq $null) {
    # do something if no rows
}
Else If (@($MyResult).Count -eq 1) {
    # do something else if there are 1 rows.
    # The cast to array was only in the if-test, 
    # so you can reach the object with $myresult.
}
Else {
    # do this if there are multiple rows.
}

回答3:

I know this thread is old, but if someone else finds it on Google, this should work also on PS V5:

Replace $MyResult.Count with: ($MyResult | Measure-Object | select -ExpandProperty Count)

For Example:
If (($MyResult | Measure-Object | select -ExpandProperty Count) -eq 0)

回答4:

Looks like this question gets a lot of views, so I wanted to post how I handled this. :)

Basically, the fix for me was to change the method I was using to execute a query on SQL Server. I switched to Chad Miller's Invoke-SqlCmd2 script: TechNet: Invoke-SqlCmd2, i.e.

# --------------- 
# this code works
# ---------------

# Register the function
. .\Invoke-Sqlcmd2.ps1

# make SQL Server call & store results to an array, $MyResults
[array]$MyResults = Invoke-Sqlcmd2 -Serve
rInstance "(local)" -Query "SELECT TOP 1 * FROM sys.databases;"

If ($MyResult -eq $null) {
    # do something
}
ElseIf ($MyResult.Count -eq 1) {
    # do something else
}
Else {
    # do this instead
}

来源：https://stackoverflow.com/questions/15395510/returning-a-row-count-for-a-datarow-in-powershell

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powershell

powershell-3.0