What is a composite index?

Answer 1

You can create an index for a table to improve the performance of queries issued against the corresponding table. You can also create an index for a cluster. You can create a compositeindex on multiple columns up to a maximum of 32 columns. A composite index key cannot exceed roughly one-half (minus some overhead) of the available space in the data block.

Use the SQL command CREATE INDEX to create an index. CREATE INDEX emp_ename ON emp_tab(ename);