Relate multiple columns

I need to relate tables based on combined columns:

DATABASE A
Table a

Column 'Trakt'
LERDAL
Column 'Blockenhet'
22:15

SHAPEFILE B
Attributetable

Column 'strFastbeteckningTrakt'
LERDAL
Column 'strFastbeteckningBlock'
22
Column 'strFastbeteckningTecken'
:
Column 'intFastbeteckningEnhet'
15

From db A, table a i want to relate columns Trakt and Blockenhet together ('LERDAL 22:15') to columns strFastbeteckningTrakt, strFastbeteckningBlock, strFastbeteckningTecken and intFastbeteckningEnhet together ('LERDAL 22:15') from Shapefile B, attributetable.

Is this possible? One solution is of course to add additional columns to both tables with the combinated column data but this will be alot of work since i have a ton of data which i often need to update.