Depends on the Sambucus and the size of the container. Remember this is a tree and can grown to 6 metres

1. The pot would definately have to be about 2' diameter aswell as depth.
2. If it actually succeeded in it you'd be forever pruning it, so, if you're growing it for the flowers or the berries you'd not get them because they'd have been pruned long since.
I'm going to presume you're buying the bronze leaved one for its attractive foliage - S. nigra 'Black Lace' ..... i have this one and as Moon Grower said, their rate of growth is very very fast.

I have just decided to move my S.nigra'Black Lace' in the Autumn as I am forever cutting it back in a large pot! I like it on the patio but it is not practical...not any longer as I don't get the berries or the flowers.

There you have it, Guest, nothing better than going by someone elses experience.