Using Powershell and a simple script to execute Sp_Cycle_Errorlog, I now have a weekly, Windows scheduled task which executes the sproc to cycle the logs for all my SQL Servers.

foreach ($svr in get-content D:\Scripts\Servers.TXT ){
    $svr
    Invoke-Expression 'SQLCMD -E -S $svr -Q "Exec Sp_Cycle_Errorlog"' | Out-Null
	}

I found a good PowerShell script for backing up databases at this blog location. However, I wanted to change it slightly to accommodate backing up ALL, System, User, or a list of databases. Processing ALL, System, or User is straightforward enough but I had to it was the first time I came up against have to compare a value against a list of values. In SQL you simply use an IN operator with a list of values but I was not sure of how to accomplish the same process in PowerShell.

Here was my problem: the user could supply a list of databases to backup and the backup script has a line with captures all the database objects for that SQL Server instance. I need to backup only those which are in the users list.

I found that the PowerShell WHERE clause can use a -contains operator which effectively filters the selection for an array. To test the operation I set up a small script to build two arrays and then I piped one array through a WHERE filter of which the results are piped to a ForEach. The ForEach sees only the results of the WHERE which mimics the SQL IN operator.

Run this code in PowerShell to see what I mean.

$a = @("db1","db2","db3","db4")
$d = @("db1","db2","db3","db4","db5","db6","db7","db8")
$d | where { $a -contains $_ } | foreach { Write-Host $_ }

$a represents the list of database supplied by the user.
$d represents the array of databases returned when accessing the Microsoft.SqlServer.Management.Smo.Server object.
I can now back up the user supplied databases within the foreach script block.

Tips & Tricks Using Compare-Object – Dreaming in PowerShell – PowerShell.com

I am very new to PowerShell but I am beginning to like using it considerably more each day. I recently had a need for a quick and easy way to script a process which would copy only new files from one location to another. after scouring the Internet for a good example, I stumbled upon the Compare-Object cmdlet and this excellent article.

The actual script I came up with is rather simple and serves my purpose exactly. As I  mentioned, I am new to PowerShell and there may very well be a better method. However, this one works for me.

The script code:

param(
    [string]$s = '\\serverx\c$\ProgramData\Polaris\3.5\SQLVS1\AuthorityUpdates',
    [string]$t = '\\servery\data03\shared\libraries\zmarc'
)

$target = Get-ChildItem $t
$source = get-childitem $s
Compare-Object $source $target -Property Name -PassThru |
    Where-Object { $_.SideIndicator -eq '<=' } |
    foreach-object -process{
        copy-item $_.FullName -destination $t
        }

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