PostgreSQL database

PostgreSQL, often simply Postgres, is an object-relational database management system (ORDBMS). It is released under a BSD-style license and is thus free and open source software. As with many other open source programs, PostgreSQL is not controlled by any single company, but has a global community of developers and companies to develop it.

Features

• Referential integrity constraints including foreign key constraints, column constraints, and row checks
• Views. Although views are by default not updateable, they can be made so by creating "insert", "update", and/or "delete" Query Re-Write Rules on the view.
• Inner, outer (full, left and right), and cross joins
• Sub-selects
• Correlated sub-queries
• Transactions
• Supports most of the major features of SQL:2008 standard
• Encrypted connections via SSL
• Binary and textual large-object storage
• Online backup
• Domains
• Tablespaces
• Savepoints
• Point-in-time recovery
• Two-phase commit
• TOAST (The Oversized-Attribute Storage Technique) is used to transparently store large table attributes (such as big MIME attachments or XML messages) in a separate area, with automatic compression. Regular expressions
• Common table expressions
• Embedded SQL is implemented using preprocessor. SQL code is first written embedded into C code. Then code is run through ECPG preprocessor, which replaces SQL with calls to code library. Then code can be compiled using C compiler. Embedding works also with C++ but it does not recognize all C++ constructs.

source: Wikipedia