In HSQLDB, you can create indexes using the CREATE INDEX SQL statement. Indexes help improve query performance by allowing the database to quickly locate rows based on the values of indexed columns. Here's the basic syntax for creating an index in HSQLDB:

CREATE INDEX index_name ON table_name (column1, column2, ...);?

Replace index_name with the desired name for your index, table_name with the name of the table you want to create the index on, and column1, column2, etc., with the names of the columns you want to include in the index. You can create indexes on one or more columns, and you can include multiple columns in a single index.


Here's an example of creating a simple index on a single column:

CREATE INDEX idx_lastname ON Employee (last_name);?

This creates an index named idx_lastname on the last_name column of the Employee table. You can also create composite indexes on multiple columns to improve the performance of queries that involve those columns. Here's an example of creating a composite index on two columns:

CREATE INDEX idx_firstname_lastname ON Employee (first_name, last_name);?

This creates an index named idx_firstname_lastname on the first_name and last_name columns of the Employee table.

After creating an index, the database automatically maintains the index whenever data in the indexed columns is inserted, updated, or deleted. Indexes can significantly improve the performance of queries that involve indexed columns, especially for large datasets or queries with selective criteria. However, keep in mind that indexes come with overhead in terms of storage space and maintenance, so you should carefully consider the columns to index based on your application's query patterns and performance requirements.