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A relational system may support several languages and various modes of terminal use (for example, the fill-in-the-blanks mode). However, there must be at least one language whose statements are expressible, per some well-defined syntax, as character strings and that is comprehensive in supporting all
58:
Codd originally set out the rules in 1970, and developed them further in a 1974 conference paper. His aim was to prevent the vision of the original relational database from being diluted, as database vendors scrambled in the early 1980s to repackage existing products with a relational veneer. Rule 12
62:
While in 1999, a textbook stated "Nowadays, most RDBMSs ... pass the test", another in 2007 suggested "no database system complies with all twelve rules." Codd himself, in his book "The
Relational Model for Database Management: Version 2", acknowledged that while his original set of 12 rules can be
118:
Null values (distinct from the empty character string or a string of blank characters and distinct from zero or any other number) are supported in fully relational DBMS for representing missing information and inapplicable information in a systematic way, independent of data
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If a relational system has a low-level (single-record-at-a-time) language, that low level cannot be used to subvert or bypass the integrity rules and constraints expressed in the higher level relational language
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The foundation rule: For any system that is advertised as, or claimed to be, a relational data base management system, that system must be able to manage data bases entirely through its relational capabilities.
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The data base description is represented at the logical level in the same way as ordinary data, so that authorized users can apply the same relational language to its interrogation as they apply to the regular
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Application programs and terminal activities remain logically unimpaired when information-preserving changes of any kind that theoretically permit unimpairment are made to the base tables.
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Integrity constraints specific to a particular relational data base must be definable in the relational data sublanguage and storable in the catalog, not in the application programs.
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The capability of handling a base relation or a derived relation as a single operand applies not only to the retrieval of data but also to the insertion, update and deletion of data.
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Each and every datum (atomic value) in a relational data base is guaranteed to be logically accessible by resorting to a combination of table name, primary key value and column name.
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The end-user must not be able to see that the data is distributed over various locations. Users should always get the impression that the data is located at one site only.
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Application programs and terminal activities remain logically unimpaired whenever any changes are made in either storage representations or access methods.
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All information in a relational data base is represented explicitly at the logical level and in exactly one way – by values in tables.
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used for coarse distinctions, the 333 features of his
Relational Model Version 2 (RM/V2) are needed for distinctions of a finer grain.
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Transact-SQL Programming: Covers
Microsoft SQL Server 6.5 /7.0 and Sybase Adaptive Server 11.5
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All views that are theoretically updatable are also updatable by the system.
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Krishna, S. (1992). "Criteria for
Evaluating Relational Database Systems".
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50:(RDBMS). They are sometimes referred to as "Codd's Twelve Commandments".
549:. Computer Science. Vol. 28. World Scientific. pp. 91 et seq.
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Codd, Edgar Frank (21 October 1985), "Does Your DBMS Run By the Rules",
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Codd, Edgar Frank (14 October 1985), "Is Your DBMS Really
Relational?",
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Microsoft Office Access 2007: The L Line, The
Express Line to Learning
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was particularly designed to counter such a positioning.
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The relational model for database management: Version 2
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The
Relational Model for Database Management: Version 2
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Transaction boundaries (begin, commit and rollback).
547:
Introduction to
Database and Knowledge-Base Systems
405:Kline, Kevin; Gould, Lee; Zanevsky, Andrew (1999).
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208:Possible for high-level insert, update, and delete
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168:Data manipulation (interactive and by program).
479:. Addison-Wesley Longman Publishing Co., Inc.
38:, designed to define what is required from a
528:Relational Database Design Clearly Explained
526:Harrington, Jan L. (2002). "Codd's Rules".
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42:in order for it to be considered
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286:(multiple-records-at-a-time).
206:Relational Operations Rule /
134:based on the relational model
22:are a set of thirteen rules (
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222:Physical data independence
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40:database management system
16:Relational database design
264:Distribution independence
236:Logical data independence
368:Cowley, Stewart (2017).
157:of the following items:
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473:Codd, Edgar F. (1990).
319:. RelDB.org. 2019-06-30
24:numbered zero to twelve
439:Hess, Kenneth (2007).
250:Integrity independence
171:Integrity constraints.
98:guaranteed access rule
30:, a pioneer of the
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511:. Addison-Wesley.
279:nonsubversion rule
317:"Codd's 12 Rules"
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458:22 January
424:22 January
387:22 January
323:August 14,
303:References
46:, i.e., a
44:relational
36:databases
507:(1990).
291:See also
275:Rule 12:
261:Rule 11:
247:Rule 10:
127:Dynamic
233:Rule 9:
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132:catalog
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54:History
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129:online
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67:Rules
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389:2022
376:ISBN
325:2020
277:The
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188:The
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