I have too many servers to manage to want to do this manually on each server so I'd like to somehow automate this using the dbatools module and the below query for gathering the backupset information.

```
  WITH BackupsSize AS(
  SELECT TOP 1000
         rn = ROW_NUMBER() OVER (ORDER BY DATEPART(year,[backup_start_date]) ASC, DATEPART(month,[backup_start_date]) ASC)
    , [Year]  = DATEPART(year,[backup_start_date])
    , [Month] = DATEPART(month,[backup_start_date])
    , [Backup Size GB] = CONVERT(DECIMAL(10,2),ROUND(AVG([backup_size]/1024/1024/1024),4))
    , [Compressed Backup Size GB] = CONVERT(DECIMAL(10,2),ROUND(AVG([compressed_backup_size]/1024/1024/1024),4))
FROM 
    msdb.dbo.backupset
WHERE 
    [database_name] = N'A1000370D1'
AND [type] = 'D'
AND backup_start_date BETWEEN DATEADD(mm, - 13, GETDATE()) AND GETDATE()
GROUP BY 
    [database_name]
    , DATEPART(yyyy,[backup_start_date])
    , DATEPART(mm, [backup_start_date])
ORDER BY [Year],[Month]) 
--SECTION 1 END

--SECTION 2 BEGIN
SELECT 
   b.Year,
   b.Month,
   b.[Backup Size GB],
   0 AS deltaNormal,
   b.[Compressed Backup Size GB],
   0 AS deltaCompressed
FROM BackupsSize b
WHERE b.rn = 1
UNION
SELECT 
   b.Year,
   b.Month,
   b.[Backup Size GB],
   b.[Backup Size GB] - d.[Backup Size GB] AS deltaNormal,
   b.[Compressed Backup Size GB],
   b.[Compressed Backup Size GB] - d.[Compressed Backup Size GB] AS deltaCompressed
FROM BackupsSize b
CROSS APPLY (
   SELECT bs.[Backup Size GB],bs.[Compressed Backup Size GB]
   FROM BackupsSize bs
   WHERE bs.rn = b.rn - 1
) AS d

```

I have a list of servers sitting in table on a db and plan to load a $sqlinstance variable with my list of instances using invoke-dbaquery.

What I'm not sure about and need help with is how to use the above SQL script to gather the historical backup data for all databases on all servers in one go. How can I loop through each database while also looping through my list of instances?