Monday, 2 March 2015

Codd's Twelve Rules - Rule 11 - Distribution Independence

Codd's Twelve Rules - Rule 11 - Distribution Independence Rule



Rule 11
Distribution Independence
Rule
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.
Description
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.
Example
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.
Some DBMS that fulfills this property
SQL Server, Oracle, MySQL, IBM DB2


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