Codd's Twelve Rules - Rule 11 - Distribution Independence Rule
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Rule 11
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Distribution Independence
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Rule
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The
data manipulation sub-language of a relational DBMS must enable application
programs and terminal activities to remain logically unimpaired whether and
whenever data are physically centralized or distributed.
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Description
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The
distribution of the parts of any database to different sites/locations should
be invisible to the end users. That is, like in distributed database it
should give a centralized effect to the end users who access it.
Also,
the existing applications are able to continue their operations when the database
is distributed or redistributed.
This
way of execution provides parallelism in handling transactions.
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Example
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Oracle
CREATE
TABLE sales_hash(salesman_id
NUMBER(5), salesman_name VARCHAR2(30), sales_amount NUMBER(10), week_no NUMBER(2)) PARTITION BY
HASH(salesman_id) PARTITIONS 4 STORE IN (ts1, ts2, ts3, ts4);
The table sales_hash will be created with 4
partitions on salesman_id values,
and partitions will be stored in tablespaces ts1, ts2, ts3, and ts4.
MySQL
CREATE
TABLE Emp(Eid INT, EName VARCHAR(30), Salary INT, Dno INT) ENGINE = INNODB
PARTITION BY HASH(Dno) PARTITIONS 6;
The above statement
creates a table Emp with 6
partitions on Dno attribute values.
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Some DBMS that fulfills this property
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SQL Server, Oracle,
MySQL, IBM DB2
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