Do i need to animate both sword and arm for attack animation?

I need a help in animation that i want my character to swing a sword when button pressed so i have animated an character hand and have a sword without animation do i also need to animate sword too? in Unrealengine4 one dont need to animate weapon but just animate the hand and attach weapon to it and it will move as with hand but what about unity3d? if i attach a weapon to him and animate the both thing. the problem he will be imported with weapon but i dont want that because i want him to hold all kinds of collectable stuff and so please give me a tip how to make this? and the animations are done in blender

 

No, you don't not to animate the sword or import it with character. Once you import your character into scene, you'll see a skeleton hierarchy in hierarchy panel. Expand it down to your hand joint and place all your weapons under it. Then with script you can enable mesh renderer for weapon you want to see and disable for weapons you don't want to see.
Renderer.enable