How to add an index to a table in Oracle?

To add an index to a table in Oracle, you can use the following syntax:

CREATE INDEX index_name
ON table_name (column_name);

index_name is the name of the index, table_name is the name of the table where the index needs to be added, and column_name is the name of the column to be indexed.

For example, we want to add an index to the table named employees that will be sorted based on the last_name column.

CREATE INDEX idx_lastname
ON employees (last_name);

Please note that adding indexes can impact the performance of a table, so it is important to carefully select which columns need indexing. Typically, indexes should be used on columns that are frequently used for searching, sorting, and joining operations.