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Halloween Problem
In computing, the Halloween Problem refers to a phenomenon in databases in which an update operation causes a change in the physical location of a row, potentially allowing the row to be visited again later in the same update operation. This could even cause an infinite loop in some cases where updates continually place the updated record ahead of the scan performing the update operation. The potential for this database error was first discovered by Don Chamberlin, Pat Selinger, and Morton Astrahan in 1976, on Halloween Halloween or Hallowe'en (less commonly known as Allhalloween, All Hallows' Eve, or All Saints' Eve) is a celebration observed in many countries on 31 October, the eve of the Western Christian feast of All Saints' Day. It begins the observanc ... day while working on a query that was supposed to give a ten percent raise to every employee who earned less than $25,000. This query would run successfully, with no errors, but when finished all the employees in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance. A database management system (DBMS) is the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS software additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an appli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Update (SQL)
An SQL UPDATE statement changes the data of one or more records in a table. Either all the rows can be updated, or a subset may be chosen using a condition. The UPDATE statement has the following form: :UPDATE ''table_name'' SET ''column_name'' = ''value'' ''column_name'' = ''value ...'' ''WHERE ''condition'' For the UPDATE to be successful, the user must have data manipulation privileges (UPDATE privilege) on the table or column and the updated value must not conflict with all the applicable constraints (such as primary keys, unique indexes, CHECK constraints, and NOT NULL constraints). In some databases, such as PostgreSQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table. When using FROM, one should ensure that the join produces at most one output row for each row to be modified. In other words, a target r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Don Chamberlin
Donald D. Chamberlin is an American computer scientist who is one of the principal designers of the original SQL language specification with Raymond F. Boyce, Raymond Boyce. He also made significant contributions to the development of XQuery. Chamberlin was elected a member of the National Academy of Engineering in 1997 for contributions to the SQL database query language. Biography Donald D. Chamberlin was born in San Jose, California. After attending Campbell High School (Campbell, California), Campbell High School, he studied engineering at Harvey Mudd College from where he holds a BS. After graduating, he went to Stanford University on a National Science Foundation grant. At Stanford, he studied electrical engineering and minored in computer science. Chamberlin holds an MSc and a PhD degree in electrical engineering from Stanford University. After graduating, Chamberlin went to work for IBM Research at the Yorktown Heights research facility in New York, where he had previous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pat Selinger
Patricia G. Selinger is an American computer scientist and IBM Fellow, best known for her work on relational database management systems. Education She received A.B. (1971), S.M. (1972), and Ph.D. (1975) degrees in applied mathematics from Harvard University. Biography She played a fundamental role in the development of System R, a pioneering relational database implementation, and wrote the canonical paper on relational query optimization. She is a pioneer in relational database management and inventor of the technique of cost-based query optimization. She was a key member of the original System R team that created the first relational database research prototype. The dynamic programming algorithm for determining join order proposed in that paper still forms the basis for most of the query optimizers used in modern relational systems. She also established and led IBM’s Database Technology Institute, considered one of the most successful examples of a fast technology pipe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morton Astrahan
Morton may refer to: People * Morton (surname) * Morton (given name) Fictional * Morton Koopa, Jr., a character and boss in ''Super Mario Bros. 3'' * A character in the ''Charlie and Lola'' franchise * A character in the 2008 film '' Horton Hears a Who'' * Morton Slumber, a funeral director who assists the diamond smuggling ring in '' Diamonds Are Forever'' * Morton "Mort" Rainey, an author and the main character of the 2004 film ''Secret Window'' Places Canada * Rural Municipality of Morton, Manitoba, a former rural municipality * Morton, Ontario, a community in Rideau Lakes England * Morton, Carlisle, a place in Carlisle, Cumbria * Morton, Eden, Cumbria * Morton, Derbyshire * Morton, Gloucestershire * Morton, Isle of Wight * Morton, a village in Morton and Hanthorpe parish, Lincolnshire * Morton by Gainsborough, Lincolnshire * Morton Hall, Lincolnshire * Morton, Norfolk (or Morton on the Hill) * Morton, Nottinghamshire * Morton-on-Swale, North Yorkshire * Morton, Shrop ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halloween
Halloween or Hallowe'en (less commonly known as Allhalloween, All Hallows' Eve, or All Saints' Eve) is a celebration observed in many countries on 31 October, the eve of the Western Christian feast of All Saints' Day. It begins the observance of Allhallowtide, the time in the liturgical year dedicated to remembering the dead, including saints ( hallows), martyrs, and all the faithful departed. One theory holds that many Halloween traditions were influenced by Celtic harvest festivals, particularly the Gaelic festival Samhain, which are believed to have pagan roots. Some go further and suggest that Samhain may have been Christianized as All Hallow's Day, along with its eve, by the early Church. Other academics believe Halloween began solely as a Christian holiday, being the vigil of All Hallow's Day. Celebrated in Ireland and Scotland for centuries, Irish and Scottish immigrants took many Halloween customs to North America in the 19th century,Brunvand, Jan (editor). ''Ame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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