Oracle Index: CREATE, DROP, RENAME — Guide with Examples
With Oracle indexes, users can access the data they need much faster and easier. However, it is essential to have a good understanding of indexes in Oracle because, depending on the commands in which they are used, they can both speed up and slow down the work. For example, in SELECT statements, using indexes can significantly improve overall performance. While in INSERT, UPDATE, and DELETE commands, indexes slow down the execution of operations.
How to use Oracle CREATE INDEX statement?
Indexes are independent of tables — we can create or drop them as needed — this will not affect tables and other indexes. But it is important to remember that the more indexes you have and the larger they are, the more memory they will take up.
The default index created in Oracle is not a unique B-Tree index. To create a new one, use the CREATE INDEX command with the following syntax:
CREATE INDEX index_name
ON table_name(column1,column2, …columnN);
To improve the performance of queries containing functions in WHERE clauses, use function-based indexes. To tell Oracle to create a function-based index on your table, the following syntax is used:
CREATE [UNIQUE] INDEX index_name
ON table_name(function1, function2, … functionN);
How to rename an index in Oracle?
Quite often, when working with Oracle, you may need to change the name of an index. If the user has the ALTER right on the index, the task is simple (if not, check with the administrators).
The Oracle alter index rename command looks like this:
CHANGE INDEX current_index_name
RENAME TO new_index_name;
Renaming an index does not affect columns or tables.
How to drop an index in Oracle?
The DROP INDEX command in Oracle allows users to drop any existing index from the current database schema.
This will not affect the table because indexes are independent objects and are stored separately. However, you will need to check if you can still use this index in some queries. In this case, queries using the dropped index will take longer to complete.
The statement to drop an Oracle index:
DROP INDEX [schema_name.]index_name;
Note that dropping a table also automatically removes all relevant triggers and indexes.
How to automate index management in Oracle?
Every database has many indexes, and managing them takes a long time if this work is not automated. dbForge Studio for Oracle allows you to work with indexes in Oracle in a visual mode, but this is not the only advantage of Studio — it helps you solve any tasks related to Oracle databases.
You can read a complete guide with examples on Oracle Indexes here — https://blog.devart.com/create-oracle-index.html
