How Do I Choose the Best Database Freeware?

A database is a collection of data that is stored together in a way that can be shared by multiple users, has as little redundancy as possible, and is independent of the application. It is holistic and shared.

Database software

Oracle Origin

A software company called Ampex in the 1970s was

SQL Server

A relational database system developed by IBM. DB2 is mainly used in large-scale application systems, has good scalability, can support from

Microsoft operates according to the distribution of the client / server architecture. This approach creates unnecessary cost and complexity. In the Internet, Oracle has found a better answer. In Internet Computing's multi-tiered architecture, centralization can simplify application deployment and maintenance, data management and backup, and provide customers with advanced performance, security, and reliability ?? Results Reduces overall operating costs. Oracle has the ability to store all data and documents in a few high-performance databases. This ability enables customers to centrally manage all their data, and makes information management and access easier, more reliable, and cheaper.

PostgreSQL is an open source successor to the original Berkeley code. Berkeley (BSD) 's contribution to computer science can be described as huge. Throughout the history of computer science, the researchers and students of this school have been almost everywhere. PostgreSQL supports most SQL standards and provides many other modern features: complex queries, foreign keys, triggers, views, transactional integrity, multi-version concurrency control. Similarly, PostgreSQL can be extended in many ways, for example, by adding new data types, functions, operators, aggregate functions, indexing methods, and procedural languages. And, because of the flexibility of the license, anyone can use, modify, and distribute PostgreSQL for free for any purpose, whether for private, commercial, or academic research. In 1996, it became clear that the name "Postgres95" could not stand the test of time. So we named it PostgreSQL to reflect the relationship between the original POSTGRES and the latest version using SQL. At the same time, the version numbers are restarted from 6.0, and the version numbers are returned to the original order started by the Berkeley POSTGRES project. Postgres95 development was focused on identifying and understanding existing backend code. The focus of PostgreSQL development has shifted to some controversial features and functions, of course, all aspects of work are being carried out at the same time.

A brief history of PostgreSQL

The object-relational database management system now known as PostgreSQL (sometimes called Postgres95) was developed from the POSTGRES package written by Berkeley. After more than ten years of development, PostgreSQL is the most advanced open source database system available in the world. It provides multi-version parallel control and supports almost all SQL components (including subqueries, transactions, and user-defined types and functions). And can get a very wide range of (development) language bindings (including C, C ++, Java, perl, tcl, and python).

Berkeley's POSTGRES Project

The POSTGRES project led by Michael Stonebraker is co-sponsored by the Defense Advanced Research Projects Agency (DARPA), the Army Research Office (ARO), the National Science Foundation (NSF), and ESL, Inc. The implementation of POSTGRES began in 1986, and the original concept of the system is detailed in the design of POSTGRES. For the earliest data model definitions, see The POSTGRES Data Model. The design of the rule system at that time was described in the design of the POSTGRES rule system. The theoretical basis and architecture of the storage manager are described in detail in the design of the POSTGRES storage system. Since then, POSTGRES has undergone several major version updates. The first "demonstrative" system was ready for use in 1987 and was exhibited at the ACM-SIGMOD conference in 1988. Version 1 was released for external users in June 1989. In response to user criticism of the first rule system, the author redesigned the rule system and released version 2 of the new rule system in June 1990. Version 3 appeared in 1991, added support for multiple storage managers, improved query executors, and re-written the rule system. Since then, subsequent releases until the release of Postgres95 have focused on portability and reliability.

POSTGRES has been used in many research or practical applications. These applications include: a financial data analysis system, a jet engine performance monitoring software package, an asteroid tracking database, a medical information database, and some geographic information systems. POSTGRES is also used by many universities for teaching purposes. Finally, Illustra Information Technologies Illustra Information Technologies (later merged into Informix, which now belongs to IBM) took the code and commercialized it. In late 1992, POSTGRES became the premier data manager for the Sequoia 2000 Scientific Computing Program.

By 1993, the number of external users had almost doubled. As users increase. Increasing time for source code maintenance is taking up too much time that should have been used for database research. To reduce the burden of support, Berkeley's POSTGRES project was officially terminated at version 4.2.

Database software introduction

In 1994, Andrew Yu and Jolly Chen added an interpreter for the SQL language to POSTGRES. And then posted the Postgres95 source code to the Internet for everyone to use, becoming an open source, the successor to the original Berkeley POSTGRES code.

All Postgres95 source code is fully ANSI C, and the code size is reduced by 25%. And there are many internal modifications to improve performance and maintainability of the code. Postgres95 version 1.0.x is approximately 30-50% faster than POSTGRES v4.2 when performing Wisconsin Benchmark tests. In addition to fixing some errors, here are some major improvements: The original query language PostQUEL was replaced by SQL (implemented on the server side). Subqueries were not supported before PostgreSQL) (but this feature can be implemented by user-defined SQL functions in Postgres95). Aggregation has been re-implemented. Support for GROUP BY query clauses has also been added. C programs can still call libpq interface functions.

Newly added interactive SQL query (psql) using GNU Readline. This program largely replaces the old monitor program. Added a new front-end library, libpgtcl, to support Tcl-based clients. A sample shell, pgtclsh, provides new Tcl commands for interaction between Tcl programs and the Postgres95 backend. Completely rewritten the interface for large objects. Inversion is retained as the only mechanism for storing large objects. (Inversion file system is removed.) The instance-level rule system is removed. But we can still use rules by rewriting them.

Added a short tutorial on commonly used SQL and SQL features specific to Postgres95 to the released source code. GNU make (instead of BSD make) is used for production. Postgres95 can use unpatched GCC (fixes the alignment of even data sections (doubles)).

SQLITE Database software SQLITE

File database, used by multiple embedded programs.

SQLite, a lightweight database, is ACID-compliant relational data

The library management system is designed to be embedded, and it has been used in many embedded products. It takes up very low resources. In embedded devices, it may only need a few hundred K of memory .
Although SQLite is small and exquisite, the supported SQL statements are not inferior to other open source databases, and it also supports transaction processing functions and so on.