Differentiate between B-tree and B⁺ tree   

Ans:  A B-tree (or Balanced Tree) is a search tree along with additional constraints that makes sure that the tree is all the time balanced and that the space wasted by deletion, if any, never becomes excessive. In a B-tree, each value of the search field appears just once at some level in the tree, along with a data pointer. In the B⁺-tree, data pointers are stored just only at the leaf nodes of the tree; hence, the structure of leaf nodes is different from the structure of internal nodes. The leaf nodes of the B⁺-tree are generally linked together to provide ordered access on the search field to the records. A few search field values from the leaf nodes are repeated in the internal nodes of the B⁺-tree to guide the search.