There are two ways to derive the Bernoulli equation. The first involves integration of the Euler equation, during which you assume the flow to be incompressible. The Euler equations themselves are only valid for inviscid flow by definition since they are simply the Navier-Stokes equations with the viscous terms and heat conduction terms removed. The other method is to apply conservation of energy along a streamline while ignoring the effects of heat transfer, compressibility and viscosity. Either way, you have ignored viscosity ("friction") and compressibility, so the equation itself is not valid except in incompressible, "frictionless" flows.
The steady flow energy equation makes no such assumptions.
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