What types of indexes are there in Oracle and which ones have you used?

In Oracle, there are several types of indexes used to optimize queries:

1. B-tree index — the most common type, suitable for equality and range queries. A standard balanced tree.
2. Bitmap index — effective for columns with low cardinality (few unique values), often used in analytical systems.
3. Clustered index — an index that determines the physical order of rows in a table (implemented in Oracle through indexed tables).
4. Function-based index — an index on an expression or function of a column, allowing faster queries with functions.
5. Reverse key index — reverses the bytes of the key to reduce locking during inserts into sequential keys.
6. Domain index — user-defined indexes for specific data types (e.g., text, spatial).

Which ones have you used:

• B-tree — for most main tables and columns with high cardinality.
• Bitmap — for analytical tables with columns that have few unique values (e.g., gender, status).
• Function-based — to speed up queries with functions, e.g., indexing UPPER(col).

The choice of index depends on the nature of the data and queries.