Why would this query return an error that mentions an entirely different database being offline?

Question

Trying to get a list of fragmented indexes based on a database name.  However, 
SELECT COUNT(*) AS TableFragOver80PctCount
FROM sys.dm_db_index_physical_stats (null, null, null, null, null )as ts
INNER JOIN sys.tables t on t.[object_id] = ts.[object_id]
INNER JOIN sys.indexes i on i.[object_id] = ts.[object_id]
INNER JOIN sys.databases db ON ts.database_id = db.database_id
WHERE db.name = 'MY DB NAME'
AND ts.avg_fragmentation_in_percent > 80.00
The error I get back 
Msg 942, Level 14, State 4, Line 1
Database 'VERY DIFFERENT DB' cannot be opened because it is offline.
I know there is a database on this server that is offline, actually 2 or 3, but not the one Im trying to get information about.  What could cause the above query to have trouble getting index info that is caused by an entirely different database being
offline?

Answer 1

FROM sys.dm_db_index_physical_stats (null, null, null, null, null )as ts
See MSDN sys.dm_db_index_physical_stats
;  the first parameter is the database id; if you pass NULL as here, then all databases will be scanned, also your offline one.
Olaf Helper
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