Description logics are widely used to express structured data and provide reasoning facility to query and integrate data from different databases. This paper presents a many-sorted description logic ${\cal MDL}$ to represent relational databases. We give a translation from relational databases to the description logic ${\cal MDL}$, and show this translation completely and faithfully captures the information in the relational database. Moreover, we show that some relational algebra operations could be expressed in ${\cal MDL}$.