If the author meant “dictionary” in a sense of a hash map, that’s not quite correct. In relational databases, indexes are usually B-trees, which are ordered, unlike hash maps. A B-tree can help with range-searches, ORDER BY and even merge joins, not just equality-searches.
If the author meant “dictionary” in a sense of a hash map, that’s not quite correct. In relational databases, indexes are usually B-trees, which are ordered, unlike hash maps. A B-tree can help with range-searches, ORDER BY and even merge joins, not just equality-searches.