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Savepoint
A savepoint is a way of implementing subtransactions (also known as nested transactions) within a relational database management system by indicating a point within a transaction that can be " rolled back to" without affecting any work done in the transaction before the savepoint was created. Multiple savepoints can exist within a single transaction. Savepoints are useful for implementing complex error recovery in database applications. If an error occurs in the midst of a multiple-statement transaction, the application may be able to recover from the error (by rolling back to a savepoint) without needing to abort the entire transaction. A savepoint can be declared by issuing a SAVEPOINT ''name'' statement. All changes made after a savepoint has been declared can be undone by issuing a ROLLBACK TO SAVEPOINT ''name'' command. Issuing RELEASE SAVEPOINT ''name'' will cause the named savepoint to be discarded, but will not otherwise affect anything. Issuing the commands ROLLBACK or C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rollback (data Management)
In database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed. They are crucial for recovering from database server crashes; by rolling back any transaction which was active at the time of the crash, the database is restored to a consistent state. The rollback feature is usually implemented with a transaction log, but can also be implemented via multiversion concurrency control. Cascading rollback A cascading rollback occurs in database systems when a transaction (T1) causes a failure and a rollback must be performed. Other transactions dependent on T1's actions must also be rollbacked due to T1's failure, thus causing a cascading effect. That is, one transaction's failure causes many to fail. Practical database recovery techniques guarantee cascadeless rollback, therefore a ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PostgreSQL
PostgreSQL (, ), also known as Postgres, is a free and open-source relational database management system (RDBMS) emphasizing extensibility and SQL compliance. It was originally named POSTGRES, referring to its origins as a successor to the Ingres database developed at the University of California, Berkeley. In 1996, the project was renamed to PostgreSQL to reflect its support for SQL. After a review in 2007, the development team decided to keep the name PostgreSQL and the alias Postgres. PostgreSQL features transactions with Atomicity, Consistency, Isolation, Durability (ACID) properties, automatically updatable views, materialized views, triggers, foreign keys, and stored procedures. It is designed to handle a range of workloads, from single machines to data warehouses or Web services with many concurrent users. It is the default database for macOS Server and is also available for Windows, Linux, FreeBSD, and OpenBSD. History PostgreSQL evolved from the Ingres proj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MySQL
MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database organizes data into one or more data tables in which data may be related to each other; these relations help structure the data. SQL is a language programmers use to create, modify and extract data from the relational database, as well as control user access to the database. In addition to relational databases and SQL, an RDBMS like MySQL works with an operating system to implement a relational database in a computer's storage system, manages users, allows for network access and facilitates testing database integrity and creation of backups. MySQL is free and open-source software under the terms of the GNU General Public License, and is also available under a variety of proprietary licenses. MySQL was owned and sponsored by the Swedish com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firebird (database Server)
Firebird is an open-source SQL relational database management system that supports Linux, Microsoft Windows, macOS and other Unix platforms. The database forked from Borland's open source edition of InterBase in 2000 but the code has been largely rewritten since Firebird 1.5. History Within a week of the InterBase 6.0 source being released by Borland on 25 July 2000, the Firebird project was created on SourceForge. Firebird 1.0 was released for Linux, Microsoft Windows and Mac OS X on 11 March 2002, with ports to Solaris, FreeBSD 4, HP-UX over the next two months. Work on porting the codebase from C to C++ began in 2000. On 23 February 2004, Firebird 1.5 was released, which was the first stable release of the new codebase. Version 1.5 featured an improved query optimizer, SQL-92 conditional expressions, SQL:1999 savepoints and support for explicit locking. Firebird 2.0 was released on 12 November 2006, adding support for 64-bit architectures, tables nested in FROM claus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nested Transaction
A nested transaction is a database transaction that is started by an instruction within the scope of an already started transaction. Nested transactions are implemented differently in different databases. However, they have in common that the changes are not made visible to any unrelated transactions until the outermost transaction has committed. This means that a commit in an inner transaction does not necessarily persist updates to the system. In some databases, changes made by the nested transaction are not seen by the 'host' transaction until the nested transaction is committed. According to some, this follows from the isolation property of transactions. The capability to handle nested transactions properly is a prerequisite for true component-based application architectures. In a component-based encapsulated architecture, nested transactions can occur without the programmer knowing it. A component function may or may not contain a database transaction (this is the encapsulated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relational Database Management System
A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relational database systems are equipped with the option of using the SQL (Structured Query Language) for querying and maintaining the database. History The term "relational database" was first defined by E. F. Codd at IBM in 1970. Codd introduced the term in his research paper "A Relational Model of Data for Large Shared Data Banks". In this paper and later papers, he defined what he meant by "relational". One well-known definition of what constitutes a relational database system is composed of Codd's 12 rules. However, no commercial implementations of the relational model conform to all of Codd's rules, so the term has gradually come to describe a broader class of database systems, which at a minimum: # Present the data to the user as relati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Transaction
A database transaction symbolizes a unit of work, performed within a database management system (or similar system) against a database, that is treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in a database. Transactions in a database environment have two main purposes: # To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure. For example: when execution prematurely and unexpectedly stops (completely or partially) in which case many operations upon a database remain uncompleted, with unclear status. # To provide isolation between programs accessing a database concurrently. If this isolation is not provided, the programs' outcomes are possibly erroneous. In a database management system, a transaction is a single unit of logic or work, sometimes made up of multiple operations. Any logical calculation done in a consistent mode in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Database
Oracle Database (commonly referred to as Oracle DBMS, Oracle Autonomous Database, or simply as Oracle) is a multi-model database management system produced and marketed by Oracle Corporation. It is a database commonly used for running online transaction processing (OLTP), data warehousing (DW) and mixed (OLTP & DW) database workloads. Oracle Database is available by several service providers on-prem, on-cloud, or as a hybrid cloud installation. It may be run on third party servers as well as on Oracle hardware (Exadata on-prem, on Oracle Cloud or at Cloud at Customer). History Larry Ellison and his two friends and former co-workers, Bob Miner and Ed Oates, started a consultancy called Software Development Laboratories (SDL) in 1977. SDL developed the original version of the Oracle software. The name ''Oracle'' comes from the code-name of a CIA-funded project Ellison had worked on while formerly employed by Ampex. Releases and versions Oracle products follow a custom r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microsoft SQL Server
Microsoft SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications—which may run either on the same computer or on another computer across a network (including the Internet). Microsoft markets at least a dozen different editions of Microsoft SQL Server, aimed at different audiences and for workloads ranging from small single-machine applications to large Internet-facing applications with many concurrent users. History The history of Microsoft SQL Server begins with the first Microsoft SQL Server product—SQL Server 1.0, a 16-bit server for the OS/2 operating system in 1989—and extends to the current day. Its name is entirely descriptive, it being ''server'' software that responds to queries in the '' SQL'' language. Milestones * MS SQL Server for OS/2 began as a project to port Sybase SQL Server onto O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM Db2
Db2 is a family of data management products, including database servers, developed by IBM. It initially supported the relational model, but was extended to support object–relational features and non-relational structures like JSON and XML. The brand name was originally styled as DB/2, then DB2 until 2017 and finally changed to its present form. History Unlike other database vendors, IBM previously produced a platform-specific Db2 product for each of its major operating systems. However, in the 1990s IBM changed track and produced a Db2 common product, designed with a mostly common code base for L-U-W (Linux-Unix-Windows); DB2 for System z and DB2 for IBM i are different. As a result, they use different drivers. DB2 traces its roots back to the beginning of the 1970s when Edgar F. Codd, a researcher working for IBM, described the theory of relational databases, and in June 1970 published the model for data manipulation. In 1974, the IBM San Jose Research center de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SQLite
SQLite (, ) is a database engine written in the C programming language. It is not a standalone app; rather, it is a library that software developers embed in their apps. As such, it belongs to the family of embedded databases. It is the most widely deployed database engine, as it is used by several of the top web browsers, operating systems, mobile phones, and other embedded systems. Many programming languages have bindings to the SQLite library. It generally follows PostgreSQL syntax, but does not enforce type checking by default. This means that one can, for example, insert a string into a column defined as an integer. History D. Richard Hipp designed SQLite in the spring of 2000 while working for General Dynamics on contract with the United States Navy. Hipp was designing software used for a damage-control system aboard guided-missile destroyers, which originally used HP-UX with an IBM Informix database back-end. SQLite began as a Tcl extension. In August 2000, versio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
H2 (DBMS)
H2 is a relational database management system written in Java. It can be embedded in Java applications or run in client-server mode. The software is available as open source software Mozilla Public License 2.0 or the original Eclipse Public License. History The development of the H2 database engine started in May 2004, and first published in December 2005. The database engine was written by Thomas Mueller. He also developed the Java database engine Hypersonic SQL. In 2001, the Hypersonic SQL project was stopped, and the HSQLDB Group was formed to continue work on the Hypersonic SQL code. The name H2 stands for Hypersonic 2, however H2 Does not share code with Hypersonic SQL or HSQLDB. H2 is built from scratch. Main features Use of SQL A subset of the SQL (Structured Query Language) standard is supported. The main programming APIs are SQL and JDBC, however the database also supports using the PostgreSQL ODBC driver by acting like a PostgreSQL server. Table types It is possible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
