Check if XML Node is true, and if so, execute a SQL statement - powershell

Question

I'm working on a script that reads from an XML list of environments and reiterates through each entry, restores a database, runs schema changes on the database, and then backs up said database. I have all of these pieces working, but I'd like to add logic to the script to include a step to set the DB Owner before running the schema changes if the XML node exists;
Currently, if I run this, it writes 'No DBOwner Specified' no matter what.
$dbOwnerExists = $($Environment.Backup.DatabaseBackup.DBOwner)
if ($dbOwnerExists -eq $true) {
Invoke-Sqlcmd -ServerInstance "$($DatabaseBackup.Instance)" -Query "EXEC sp_changedbowner $($Environment.Backup.DatabaseBackup.DBOwner)"
} else {
Write-Output 'No DBOwner Specified'
}
Current XML Looks like this
<Environments>
<Environment Database="exampleDatabase">
<Backup Restore="TRUE">
<DatabaseBackups Instance="SQLInstance" SrcLocation="\\Hostname\c$\temp\example.bak" DstLocation="\\Hostname\c$\temp\example.bak" DBOwner=""sa""/>
<DatabaseBackups Instance="SQLInstance" SrcLocation="\\Hostname\c$\temp\example2.bak" DstLocation="\\Hostname\c$\temp\example2.bak"/>
</Backup>
</Environment>
</Environments>
It seems that powershell doesn't like my logic to check if DBOwner exists in the XML, maybe $true is not the best way to check this?

Answer 1

I haven't seen your full code so this is the best I can do.
Let's assume that you have the XML stored in variable $XML and $XML was defined like this:
[xml]$xml = #"
<Environments>
<Environment Database="exampleDatabase">
<Backup Restore="TRUE">
<DatabaseBackups Instance="SQLInstance" SrcLocation="\\Hostname\c$\temp\example.bak" DstLocation="\\Hostname\c$\temp\example.bak" DBOwner=""sa""/>
<DatabaseBackups Instance="SQLInstance" SrcLocation="\\Hostname\c$\temp\example2.bak" DstLocation="\\Hostname\c$\temp\example2.bak"/>
</Backup>
</Environment>
</Environments>
"#
You can check whether DBOwner exists or not just by checking the value with
$XML.Environments.Environment.Backup.DatabaseBackups.DBOwner
Which with the XML would output:
"sa"
But to get a true/false value on whether it exists or not, you can use the [bool] datatype like you did in your answer:
[bool]$XML.Environments.Environment.Backup.DatabaseBackups.DBOwner
But I found a glitch with this in which it would still output true if the node didn't exist like so:
[bool]$XML.Environments.Environment.Backup.DatabaseBackups.fasdasd
True
so I changed it to this.
[bool][string]$($XML.Environments.Environment.Backup.DatabaseBackups.DBOwner).trim
Which in this case would output:
True
And to put this in an if statement since it is already a boolean you could put it in the in statement like so:
if([bool][string]$($XML.Environments.Environment.Backup.DatabaseBackups.DBOwner).trim){
Invoke-Sqlcmd -ServerInstance "$($DatabaseBackup.Instance)" -Query "EXEC sp_changedbowner $($Environment.Backup.DatabaseBackup.DBOwner)"
} else {
Write-Output 'No DBOwner Specified'
}
To test if this works we can also try doing this on something that doesn't exist like $XML.Environments.Environment.Backup.DatabaseBackups.SomethingThatDoesntExist which should return false and does like so:
[bool][string]($XML.Environments.Environment.Backup.DatabaseBackups.SomethingThatDoesntExist).trim()
False
To test the if statement we can do
if([bool][string]$($XML.Environments.Environment.Backup.DatabaseBackups.DBOwner).trim){
Write-Output "Exists"
} else {
Write-Warning 'No DBOwner Specified'
}
Which would output
Exists
and we could also test if it doesn't exist with
if([bool][string]$($XML.Environments.Environment.Backup.DatabaseBackups.fasdasd).trim){
Write-Output "Exists"
} else {
Write-Warning 'No DBOwner Specified'
}
The output would be:
WARNING: No DBOwner Specified
NOTE: The [bool]s in the if statements are unnecessary since if already converts things to booleans but I just put it in for easier understanding this would work fine too:
if([string]$($XML.Environments.Environment.Backup.DatabaseBackups.fasdasd).trim){
Write-Output "Exists"
} else {
Write-Warning 'No DBOwner Specified'
}

Answer 2

I was able to figure this out with the following, which works well enough for me!
$dbOwnerExists=$null
$dbOwnerExists = $($DatabaseBackup.DBOwner)
if ($dbOwnerExists) {
Invoke-Sqlcmd -ServerInstance "$($DatabaseBackup.Instance)" -Query "USE $($Environment.Database) EXEC sp_changedbowner '$($DatabaseBackup.DBOwner)'"
} else {
Write-Output 'No DBOwner Specified'
}