Indexes are data structures that enable fast searching of data in database tables. There are different types of indexes including B-tree, bitmap, and function-based indexes. Indexes can be unique or non-unique. Index-organized tables store data in an index structure based on the primary key, while heap-organized tables store data separately from indexes and access rows using row IDs. Proper use of indexes can improve query performance.

1. Creating and Managing Indexes

2. What is and Index?
• It is a data structure associated with a table
that enables fast searching of data.
• Indexes are schema objects that are logically
and physically independent of the data in the
objects with which they are associated.
• Indexes are structures stored in the database
that users manage using SQL statements.

3. What is an Index?
• Primary and unique keys automatically have
indexes, but create an index on a foreign key.
• Index must be created on the most frequently
columns in the table.
• Oracle Database does not index table rows in
which all key columns are null.

4. What is an Index?
• An index contains a collection of keys and
pointers.
– Keys are values built from one or more columns in
the table
– Pointer stores the address of the location where a
data block stored in the memory.

5. What is an Index?
• Composite Index
– Index based on one or more columns is called
composite index.
– Multiple indexes can exist for the same table if the
permutation of columns differs for each index.

6. What is an Index?
• Unique Indexes
– Unique indexes guarantee that no two rows of a
table have duplicate values in the key column or
columns.
– The data is sorted only by key.
• Non Unique Indexes
– Nonunique indexes permit duplicates values in the
indexed column or columns.
– The rowid is included in the key in sorted order

7. Types of Indexes
• B-tree Indexes
• Bitwise Indexes
• Function Based Indexes
• ALL_INDEXES view is used to list all the
indexes details.

8. Types of Indexes
• B-tree Indexes
– These indexes are the standard (NORMAL) index
type.
– They are excellent for primary key and highly-
selective indexes.
– Order list of values divided into ranges.
CREATE INDEX indexname
ON table_name(column)list);

9. Types of Indexes
• Bitmap Index
– In a bitmap index, the database stores a bitmap
for each index key.
– Used for the columns when the number of distinct
values is small compared to the number of table
rows.
CREATE BITMAP INDEX index_name
ON table_name (column_name);
Value Row 1 Row 2 Row 3 Row 4 Row 5 Row 6 Row 7 Row 8
Male 1 1 0 1 0 1 0 1
Female 0 0 1 0 1 0 1 0

10. Function Based Index
• Function Based Index
– A function-based index computes the value of a
function or expression involving one or more
columns and stores it in the index.
– A function-based index can be either a B-tree or a
bitmap index.
CREATE INDEX index_name
ON tablename (expression(s) [, column_list]);

11. Function Based Index
• Function Based Index
– The database only uses the function-based index
when the function is included in a query not at
INSERT or UPDATE statement.

12. Index Organised Tables
• An index-organized table is a table stored in a
variation of a B-tree index structure.
• In an index-organized table, rows are stored in
an index defined on the primary key for the
table.
• An index-organized table stores all data in the
same structure and does not need to store the
rowid.

13. Heap Organised vs Index Organised Tables
• In heap organised table,
– the rowid uniquely identifies a row.
– Primary key constraint may optionally be defined.
• In Index organised table,
– Primary key uniquely identifies a row.
– Primary key constraint must be defined.

14. Heap Organised vs Index Organised Tables
• In heap organised table,
– Individual rows may be accessed directly by rowid.
• In Index organised table
– Access to individual rows may be achieved
indirectly by primary

15. Heap Organised vs Index Organised Tables
• In heap organised table, can contain a column
of the LONG data type and LOB data types.
• In Index organised table, can contain LOB
columns but not LONG columns.

16. Heap Organised vs Index Organised Tables
• Heap organised Table

17. Heap Organised vs Index Organised Tables
• Indexed organised Table