• B-tree is essential in tables that are growing at a rate that quickly causes overflow in an ISAM structure (for example, situations where there are ever-increasing keys).

• B-tree is better when sorting on the key is required, because sequential access (for example, SELECT * FROM emp) to data in B-tree is automatic; there is no need to add a SORT clause to queries if you are sorting on the primary key. B‑tree also eliminates sorting of the joining column when joining on key columns; sort-merge queries are more efficient if the tables joined are B-tree.