Download HSQLDB

HSQLDB is the leading SQL Relational database engine written in Java. It has a JDBC driver and supports a rich subset of ANSI-92 SQL (BNF tree format) plus SQL 99 and 2003 enhancements. It offers a small (less than 100k in one version for applets), fast database engine which offers both in-memory and disk-based tables and supports embedded and server modes. Additionally, it includes tools such as a Minimal web server, in-memory query and management tools (can be run as applets) and a number of demonstration examples.
Features Summary
SQL

* Relational Database Management System, which can store Serializable Java objects
* Very extensive support for SQL:2008 Standard syntax, including most optional features
* Supports all base data types of the SQL Standard, including BINARY, BIT, BOOLEAN, date-time, INTERVAL, BLOB, CLOB
* Supports user-defined DOMAIN types, including type constraints
* Fast SELECT, INSERT, DELETE, UPDATE and MERGE operations
* INNER, LEFT OUTER, RIGHT OUTER and FULL joins
* NATURAL, USING and UNION joins
* UNION, EXCEPT, Intersect, including use of parentheses, limits and offsets, ALL, DISTINCT and CORRESPONDING keywords
* Scalar (single value) SELECTS, row and correlated subqueries including IN, EXISTS, ANY, ALL
* Views, Temp tables and sequences
* Updatable views
* Primary key, unique and check constraints on single or multiple columns
* Referential Integrity (foreign keys) on multiple columns with full cascading options (delete, update, set null, set default)
* ORDER BY, GROUP BY and HAVING
* COUNT, SUM, MIN, MAX, AVG and statistical aggregate functions

new:
Fully multithreaded core supports 2PL (two-phased locking) and MVCC (multiversion concurrency control). Transactions can be SERIALIZABLE or READ COMMITTED, using strict 2PL concurrency control. adds SNAPSHOT ISOLATION and READ CONSISTENCY, which are comparable to REPEATABLE READS and READ COMMITTED isolation levels.