Advantages of Binary Search Trees over Hash Tables

Question

What are the advantages of binary search trees over hash tables?

Hash tables can look up any element in Theta(1) time and it is just as easy to add an element....but

Answer 1

If you want to access the data in a sorted manner, then a sorted list has to be maintained in parallel to the hash table. A good example is Dictionary in .Net. (see http://msdn.microsoft.com/en-us/library/3fcwy8h6.aspx).

This has the side-effect of not only slowing inserts, but it consumes a larger amount of memory than a b-tree.

Further, since a b-tree is sorted, it is simple to find ranges of results, or to perform unions or merges.