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Part I is an informal introduction for new users.
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Part II documents the SQL query language environment, including data types and functions, as well as user-level performance tuning. Every PostgreSQL user should read this.
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Part III describes the installation and administration of the server. Everyone who runs a PostgreSQL server, be it for private use or for others, should read this part.
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Part IV describes the programming interfaces for PostgreSQL client programs.
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Part V contains information for advanced users about the extensibility capabilities of the server. Topics are, for instance, user-defined data types and functions.
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Part VI contains reference information about SQL commands, client and server programs. This part supports the other parts with structured information sorted by command or program.
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Part VII contains assorted information that may be of use to PostgreSQL developers.
PostgreSQL is an object-relational database management system (ORDBMS) based on POSTGRES, Version 4.2
, developed at the University of California at Berkeley Computer Science Department. POSTGRES pioneered many concepts that only became available in some commercial database systems much later.
PostgreSQL is an open-source descendant of this original Berkeley code. It supports a large part of the SQL standard and offers many modern features:
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complex queries
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foreign keys
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triggers
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views
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transactional integrity
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multiversion concurrency control
Also, PostgreSQL can be extended by the user in many ways, for example by adding new
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data types
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functions
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operators
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aggregate functions
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index methods
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procedural languages
And because of the liberal license, PostgreSQL can be used, modified, and distributed by everyone free of charge for any purpose, be it private, commercial, or academic.