What is postgresql?

PostgreSQL is a free object-relational database server (database management system) released under a flexible BSD-style license. It provides an alternative to other open source database systems (such as MySQL and Firebird), and proprietary systems (such as Oracle, Sybase, IBM's DB2 and Microsoft SQL Server).

PostgreSQL's unusual name causes some readers to stop and try to pronounce it, especially those who pronounce SQL as "sequel." PostgreSQL developers pronounce it "post-gress-Q-L". It is also often pronounced simply as "postgres".

In fact, the features of PostgreSQL cover SQL-2/SQL-92 and SQL-3/SQL-99. First of all, it includes support for arguably the richest data types in the world, including It can be said that some data types are not even available in commercial databases, such as IP types and geometric types. Secondly, PostgreSQL is a full-featured free software database. For a long time, PostgreSQL has been the only system that supports transactions, subqueries, and multi-version parallel control systems. (MVCC), data integrity checking and other features is the only free software database management system. This uniqueness was broken only after vendors such as Inprise's InterBase and SAP opened their original proprietary software to free software. Finally, PostgreSQL has a very active development team, and thanks to the efforts of many hackers, the quality of PostgreSQL is improving day by day.

From a technical point of view, PostgreSQL uses a relatively classic C/S (client/server) structure, that is, a client corresponds to a server-side daemon process. This daemon analyzes the client to query request, generate a planning tree, perform data retrieval and finally format the results and output them back to the client. In order to facilitate the writing of client programs, the database server provides a unified client C interface. Different client interfaces are derived from this C interface, such as ODBC, JDBC, Python, Perl, Tcl, C/C, ESQL, etc. It should also be pointed out that PostgreSQL's support for interfaces is also very rich, almost All types of database client interfaces are supported. This can also be said to be a major advantage of PostgreSQL.

Architecture

One reason PostgreSQL is strong comes from its architecture. Like commercial databases, PostgreSQL can be used in a C/S (client/server) environment. This has many benefits for users and developers.

The core of PostgreSQL installation is the database server process. It is allowed on a dedicated server. Applications that need to access data stored in a database must go through the database process. These client programs cannot access the data directly, even if they are on the same machine as the service program.

The above is the detailed content of What is postgresql?. For more information, please follow other related articles on the PHP Chinese website!