If we want to restore database with differential backup then first we need to restore associated fill backup with NORECOVERY option.
Below is example…

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RESTORE DATABASE AdventureWorks FROM DISK = ‘C:\AdventureWorks.BAK’

WITH NORECOVERY

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Only after that we can apply Differential backup on the database…

Below is the example…
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RESTORE DATABASE AdventureWorks FROM DISK = ‘C:\AdventureWorks_Diff.BAK’

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