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| Rule 1: The Information |
All information in a relational
database is represented explicitly at the logical level and in exactly one way -
by values in tables.
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| Rule 2: Guaranteed Access |
Each and every datum (atomic value) in
a relational database is guaranteed to be logically accessible by resorting to a
combination of table name, primary key value, and column name.
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| Rule 3: Systematic Treatment of Null
Values |
Null values (distinct from the empty
character string of blank characters and distinct from any zero or other
numbers) are supported in fully relational DBMS for representing missing
information and inapplicable information in a systematic way.
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| Rule 4: Dynamic Online Catalog Based
on the Relational Model |
The database 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 data.
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| Rule 5: Comprehensive Data
Sub-language |
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,
d that is comprehensive in supporting all of the following items:
- Data Definition
- View Definition
- Data manipulation (interactive and by program)
- Integrity Constraints
- Authorization
- Transaction boundaries (begin, commit, and
rollback)
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| Rule 6: View Updating |
All views that are theoretically
updateable are also updateable by the system.
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| Rule 7: High-Level Insert, Update, and
Delete |
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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| Rule 8: Physical Data Independence |
Application programs and terminal
activities remain logically unimpaired whenever any changes are made in either
storage representations or access methods.
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| Rule 9: Logical Data Independence |
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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| Rule 10: Integrity Independence |
Integrity constraints specific to a
particular relational database must be definable in the relational data
sub-language and storable in the catalog, not in the application programs.
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| Rule 11: Distribution Independence |
A relational DBMS has distribution
dependence.
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| Rule 12: Nonsubversion |
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 (multiple records at a time).
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