Electric Potential Inside Uniformly Charged Sphere

I wanted to know how to find the electric potential inside a uniformly charged sphere of radius R. What i understand is that my textbook uses a reference point as infinity and then expresses the potential as the difference of 2 integrals.

Sooo,

V(r)= -∫E dr and the electric field is k(qr)/R^3 r is where you are from the centre of the sphere.

So the method I have seen is
. . . . r. . . . . . . . . . . . . . . . R
V = - ∫ (1/(4πεo)) qr/R³ dr - ∫ (1/(4πεo)) q/r² dr
. . . .R. . . . . . . . . . . . . . . .∞

but I was wondering if there is a way to express it as one integral from 0-R
like
. . . . R. . . . . . . . . . . . . . . .
V = - ∫ (1/(4πεo)) qr/R³ dr
. . . .o. . . . . . . . . . . . . . . .

but this of course produces a different answer. Where am I wrong in my thinking?