Oracle 11g: Indexes

How Indexes Being Created?

• Automatically
• When we created Primary Key 
• Manually

Guidelines To Create Index

• A column has wide range values
• A column has large number of null values
• One or more columns are frequently used together (Clause/Join Condition) 
• Large Table

===>  SQL Queries:  Create New Index
create index emp_last_name_idx
on employees(last_name);

Results
create index succeeded.


===> SQL Queries:  Removing an Index
drop index emp_last_name_idx;


Results:

drop index emp_last_name_idx succeeded.