Let $f,g \in L^{2}(\mathbb R)$. Suppose that $\int_{\mathbb R} |f(t)|^{2} dt \leq \int_{\mathbb R} |g(t)|^{2} dt.$
We also assume that support of $f$ and support of $g$ are equal.
My Question is: Can we say $\int_{0}^{1} |f(t)|^{2} dt \leq \int_{0}^{1} |g(t)|^{2} dt$ ?
No, certainly not. Just consider $f=2\cdot 1_{[0,1]}+1_{[2,10]}$ and $g=1_{[0,1]}+1000\cdot 1_{[2,10]}$.