I know, if $G$ ist the cyclic group of order $p$ ($p$ odd), that the simple $\mathbb{Q}G$ modules are $\mathbb{Q}$ and $\mathbb{Q}(\zeta_p)$. In that way I get the irreducible representations of the cyclic group $C_p$ over $\mathbb{Q}$.
Is there a similar way to get the irreducible representations of the dihedral group $D_p$ with $2p$ Elements over $\mathbb{Q}$, or rather all simple $\mathbb{Q}D_p$ modules?