What is Index and its types with example?

Index:-
        Index is a schema object. Index is a performance-tuning method. Using Index retrieval of data from database is fast.
       
Syntax:-
        CREATE INDEX index_name
        ON table_name(column_name1,column_name2,column_name3,...);
       
       
Rename an INDEX:-
                Alter INDEX old_index_name
                RENAME TO new_index_name;

Drop an INDEX:-
                DROP INDEX index_name;
               
               
Type of Index:-

1. Normal Index(B-Tree Index)
2. Bitmap Index
3. Function-based Index

Normal Index:-
                It is also called B-TREE Index, By Default B-TREE index is created. It manage data in tree form.
               
Bitmap Index:-
                Bitmap index put on that column which contain low cardinality. Low Cardinality means more duplicate data and less unique data.
               
Function-Based Index:-
                         The index expression can be an arithmetic expression or an expression that contains a SQL function, PL/SQL function, package function.
                           
                       
Example of Normal Index:-

                    CREATE INDEX xxc05_vendor_id
                    ON xxc05_ap_supplier(vendor_id);


Example of Bitmap Index:-

                    CREATE BITMAP INDEX xxc05_emp_gender
                    ON xxc05_employees(gender);

                   
Example of Functional Index:-

                    CREATE INDEX xxc05_vendor_id
                    ON xxc05_ap_supplier(UPPER(vendor_name));


Thanks
Sajal