Merge (SQL)

A relational database management system uses SQL MERGE (also called upsert) statements to INSERT new records or UPDATE existing records depending on whether condition matches. It was officially introduced in the SQL:2003 standard, and expanded in the SQL:2008 standard.

Usage

Right join is employed over the Target (the INTO table) and the Source (the USING table / view / sub-query). That is:

If multiple Source rows match a given Target row, an error is mandated by SQL:2003 standards. You cannot update a Target row multiple times with a MERGE statement

Implementations

Database management systems Oracle Database, DB2, Teradata, EXASOL, CUBRID, MS SQL and Vectorwise support the standard syntax. Some also add non-standard SQL extensions.

Synonymous

Some database implementations adopted the term "Upsert" (a portmanteau of update and insert) to a database statement, or combination of statements, that inserts a record to a table in a database if the record does not exist or, if the record already exists, updates the existing record. It is also used to abbreviate the "MERGE" equivalent pseudo-code.

Merge

Merge, merging, or merger may refer to:

Concepts

Computer science

Merge (software)

Merge is a software system which allows a user to run DOS/Windows 3.1 on SCO UNIX, in an 8086 virtual machine.

History

Merge was originally developed to run DOS under UNIX System V Release 2 on an AT&T 6300 Plus personal computer. Development of the virtual machine began in late 1984, and AT&T announced the availability of the machine on October 9, 1985, referring to the bundled Merge software as SimulTask. (The PC6300 Plus shipped with MS-DOS in 1985 though, because its Unix System V distribution was not ready until the end March 1986.) Merge was developed by engineers at Locus Computing Corporation, with collaboration from AT&T hardware and software engineers, particularly on aspects of the system that were specific to the 6300 Plus (in contrast to a standard PC/AT).

The AT&T 6300 Plus contained an Intel 80286 processor, which did not include the support for 8086 virtual machines (virtual 8086 mode) found in the Intel 80386 and later processors in the x86 family. On the 80286, the DOS program had to run in realmode. The 6300 Plus was designed with special hardware on the bus that would suppress and capture bus cycles from the DOS program if they were directed toward addresses not assigned for direct access by the DOS virtual machine. Various system registers, such as the programmable interrupt controller, and the video controller, had to be emulated in software for the DOS process, and a watchdog timer was implemented to recover from DOS programs that would clear the interrupt flag and then hang for too long. The hardware used the Non Maskable Interrupt (NMI) to take control back to the emulation code. More detail may be seen in the patent referenced in the External Links below.

Merge (linguistics)

Merge (usually capitalized) is one of the basic operations in the Minimalist Program, a leading approach to generative syntax, when two syntactic objects are combined to form a new syntactic unit (a set). Merge also has the property of recursion in that it may apply to its own output: the objects combined by Merge are either lexical items or sets that were themselves formed by Merge. This recursive property of Merge has been claimed to be a fundamental characteristic that distinguishes language from other cognitive faculties. As Noam Chomsky (1999) puts it, Merge is "an indispensable operation of a recursive system ... which takes two syntactic objects A and B and forms the new object G={A,B}" (p. 2).

Mechanisms of Merge

Within the Minimalist Program, syntax is derivational, and Merge is the structure-building operation. Merge is assumed to have certain formal properties constraining syntactic structure, and is implemented with specific mechanisms.

Binary branching

Merge takes two objects α and β and combines them, creating a binary structure.

SQL

SQL (ⁱ/ˈɛs kjuː ˈɛl/, or ⁱ/ˈsiːkwəl/;Structured Query Language) is a special-purpose programming language designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS).

Originally based upon relational algebra and tuple relational calculus, SQL consists of a data definition language, data manipulation language, and a data control language. The scope of SQL includes data insert, query, update and delete, schema creation and modification, and data access control. Although SQL is often described as, and to a great extent is, a declarative language (4GL), it also includes procedural elements.

SQL was one of the first commercial languages for Edgar F. Codd's relational model, as described in his influential 1970 paper, "A Relational Model of Data for Large Shared Data Banks." Despite not entirely adhering to the relational model as described by Codd, it became the most widely used database language.

SQL 2008

SQL 2008 can refer to

SQL:2006

SQL:2006 or ISO/IEC 9075:2006 standard is the fifth revision of the ISO standard for the SQL database query language.

The main changes from SQL:2003 were in the Part 14 of the standard.

Part 14

ISO/IEC 9075-14:2006 defines ways in which SQL can be used in conjunction with XML. It defines ways of importing and storing XML data in an SQL database, manipulating it within the database and publishing both XML and conventional SQL-data in XML form. In addition, it enables applications to integrate into their SQL code the use of XQuery, the XML Query Language published by the World Wide Web Consortium (W3C), to concurrently access ordinary SQL-data and XML documents.

See also