When I try restore my database backup file, I can... But I can't make new database diagram, and show the problem, below ::::
that file has copied by my university, I restore on my pc but show problem
TITLE: Microsoft SQL Server Management Studio
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Cannot execute as the database principal because the principal "dbo" does not exist, this type of principal cannot be impersonated, or you do not have permission. (Microsoft SQL Server, Error: 15517)
For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft%20SQL%20Server&ProdVer=13.00.1601&EvtSrc=MSSQLServer&EvtID=15517&LinkId=20476
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BUTTONS:
OK
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Pleasee help me fix it ???