can i use a database for smf and ipb and vbulletin

[loz04]

use the same database  for smf , ipb and vbulletin and like use it make the forums the same

[kurotenshi]

Yes you can. Set only all of them different prefix

[loz04]

cool and like they would say the same thing and be the same users

[shanks]

I'm afraid not.

They all have a different stucture to their data. You may store them all on the same database (and as already mentioned, this is best done with different prefixes), but you can't have any one system read the data of another without conversion.