Added cross tenant restore feature Lines 209 to 282

Added cross tenant restore feature Lines 209 to 282. @WilliamDAssafMSFT, please review as we discussed.

Author: ajagadish-24

articles/synapse-analytics/backuprestore/restore-sql-pool.md

@@ -206,6 +206,81 @@ $RestoredDatabase.status
 
 ```
 
+## Restore an existing dedicated SQL pool to a different tenant through PowerShell
+
+When performing a cross-tenant-subscription restore, a dedicated SQL pool in an Azure Synapse workspace can only restore directly to a standalone dedicated SQL pool (formerly SQL DW). If it is required to restore a dedicated SQL pool in an Azure Synapse workspace to a workspace in the destination subscription across a different tenant, an additional restore step is required.
+
+For cross-tenant-subscription restore, the user must have a 'GUEST' account with either the 'Owner' or 'Contributor' access permissions to the destination tenant to which the dedicated SQL pool (formerly SQL DW) will be restored to.
+
+The PowerShell script below is similar to the above, however there are three main differences:
+
+  •	After retrieving the SQL Pool object to be restored, the subscription and the tenant context needs to be switched to the destination (or target) tenant ID and subscription name or ID.
+  •	When performing the restore, use the Az.Sql modules instead of the Az.Synapse modules.
+  •	The below sample code has additional steps for restoring to an Azure Synapse workspace in the destination subscription. Uncomment the PowerShell commands as described in the sample.
+  
+Steps:
+
+1.	Open a PowerShell terminal.
+2.	Update Az.Sql Module to 3.8.0 (or greater) if needed
+3.	Connect to your Azure account and list all the subscriptions associated with your account along with its Tenant ID.
+4.	Select the subscription that contains the SQL pool to be restored.
+5.	List the restore points for the dedicated SQL pool.
+6.	Pick the desired restore point using the RestorePointCreationDate.
+7.	Create a ‘Guest’ account with either ‘Owner’ or ‘Contributor’ permissions.
+8.	Select the destination subscription along with the corresponding Tenant ID to which the SQL pool should be restored.
+9.	Restore the dedicated SQL pool to the desired restore point using Restore-AzSqlDatabase PowerShell cmdlet.
+10.	Verify that the restored dedicated SQL pool (formerly SQL DW) is online.
+11.	If the desired destination is a Synapse Workspace, uncomment the code to perform the additional restore step.
+  a.	Create a restore point for the newly created data warehouse.
+  b.	Retrieve the last restore point created by using the Select -Last 1 syntax.
+  c.	Perform the restore to the desired Azure Synapse workspace.
+
+```powershell
+$SubscriptionName="<YourSubscriptionName>"
+$TenantID= ”<Your Tenant ID>”
+$TargetSubscriptionName= ”<YourTargetSubscriptionName>”
+$TargetTenantID= ”Your Target Tenant ID>”
+$ResourceGroupName="<YourResourceGroupName>"
+$WorkspaceName="<YourWorkspaceNameWithoutURLSuffixSeeNote>“ # Without sql.azuresynapse.net
+#$TargetResourceGroupName="<YourTargetResourceGroupName>" # uncomment to restore to a different workspace.
+#$TargetWorkspaceName="<YourtargetWorkspaceNameWithoutURLSuffixSeeNote>"  
+$SQLPoolName="<YourDatabaseName>"
+$NewSQLPoolName="<YourDatabaseName>"
+
+Connect-AzAccount
+Get-AzSubscription
+Select-AzSubscription -SubscriptionName $SubscriptionName
+
+# list all restore points
+Get-AzSynapseSqlPoolRestorePoint -ResourceGroupName $ResourceGroupName -WorkspaceName $WorkspaceName -Name $SQLPoolName
+# Pick desired restore point using RestorePointCreationDate "xx/xx/xxxx xx:xx:xx xx"
+$PointInTime="<RestorePointCreationDate>"
+
+# Get the specific SQL pool to restore
+$SQLPool = Get-AzSynapseSqlPool -ResourceGroupName $ResourceGroupName -WorkspaceName $WorkspaceName -Name $SQLPoolName
+# Transform Synapse SQL pool resource ID to SQL database ID because currently the restore command only accepts the SQL database ID format.
+$DatabaseID = $SQLPool.Id -replace "Microsoft.Synapse", "Microsoft.Sql" `
+    -replace "workspaces", "servers" `
+    -replace "sqlPools", "databases"
+
+#Switch the context to the Subscription name and tenant ID to which the database would be restored to
+Set-AzContext -Subscription 'MySubscriptionName' -Tenant '00000000-0000-0000-0000-000000000000' 
+
+# Restore database from a restore point
+$RestoredDatabase = Restore-AzSynapseSqlPool –FromRestorePoint -RestorePoint $PointInTime -ResourceGroupName $SQLPool.ResourceGroupName `
+    -WorkspaceName $SQLPool.WorkspaceName -TargetSqlPoolName $NewSQLPoolName –ResourceId $DatabaseID -PerformanceLevel DW100c
+
+
+# Use the following command to restore to a different workspace
+#$TargetResourceGroupName = $SQLPool.ResourceGroupName # for restoring to different workspace in same resourcegroup 
+#$RestoredDatabase = Restore-AzSynapseSqlPool –FromRestorePoint -RestorePoint $PointInTime -ResourceGroupName $TargetResourceGroupName `
+#    -WorkspaceName $TargetWorkspaceName -TargetSqlPoolName $NewSQLPoolName –ResourceId $DatabaseID -PerformanceLevel DW100c
+
+# Verify the status of restored database
+$RestoredDatabase.status
+
+ ```
+
 ## Troubleshooting
 A restore operation can result in a deployment failure based on a "RequestTimeout" exception.