H2 is a relational database management system written in Java. It can be embedded in Java applications or run in client-server mode.
The H2 console application lets you access a SQL database using a browser interface.
An embedded web server with a browser based console application is included, as well as command line tools to start and stop a server, backup and restore databases, and a command line shell tool.
- Very fast, open source, JDBC API.
- Memory mode.
- Encrypted database, together with other strong security features such as SHA-256 password encryption, encryption functions, and SSL.
- ODBC driver.
- Fulltext search.
- Multi version concurrency.
- Disk based or in-memory databases and tables, read-only database support, temporary tables
- Transaction support (read committed), 2-phase-commit
- Multiple connections, table level locking
- Cost based optimizer, using a genetic algorithm for complex queries, zero-administration
- Scrollable and updatable result set support, large result set, external result sorting, functions can return a result set
- Embedded and server modes; in-memory databases.
- Browser based Console application.
- Small footprint: around 2 MB jar file size.
- SQL support:
- Support for multiple schemas, information schema.
- Referential integrity / foreign key constraints with cascade, check constraints.
- Inner and outer joins, subqueries, read only views and inline views.
- Triggers and Java functions / stored procedures.
- Many built-in functions, including XML and lossless data compression.
- Wide range of data types including large objects (BLOB/CLOB) and arrays.
- Sequence and autoincrement columns, computed columns (can be used for function based indexes).
- ORDER BY, GROUP BY, HAVING, UNION, OFFSET / FETCH (including PERCENT and WITH TIES), LIMIT, TOP, DISTINCT / DISTINCT ON (…).
- Window functions.
- Collation support, including support for the ICU4J library.
- Support for users and roles.
- Compatibility modes for IBM DB2, Apache Derby, HSQLDB, MS SQL Server, MySQL, Oracle, and PostgreSQL.
- Other features:
- Small footprint (around 2 MB), low memory requirements.
- Multiple index types (b-tree, tree, hash).
- Support for multi-dimensional indexes.
- CSV (comma separated values) file support.
- Support for linked tables, and a built-in virtual ‘range’ table.
- Supports the
EXPLAIN PLANstatement; sophisticated trace options.
- Database closing can be delayed or disabled to improve the performance.
- Web-based Console application (translated to many languages) with autocomplete.
- The database can generate SQL script files.
- Contains a recovery tool that can dump the contents of the database.
- Support for variables (for example to calculate running totals).
- Automatic re-compilation of prepared statements.
- Uses a small number of database files.
- Uses a checksum for each record and log entry for data integrity.
- Well tested (high code coverage, randomized stress tests).
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