Relational Data Modeling for Database Systems Part – 4
Relational Algebra
Relational algebra is a technical language containing a group of different operators. Every single operator takes one (1) or more (N) tables or relations as its input as well as yields only one (1) table or relation as its output. There are seven (7) rudimentary relational algebra operations present, which are
1. Selection, (Part – 3)
2. Projection, (Part – 3)
3. Joining, (Part – 3)
4. Union,
5. Intersection,
6. Difference and
7. Division
It is significant to remember that these above mentioned operations do not modify the database tables or relations. The table or relation formed by means of an operation is obtainable to the end user but then again it is not kept permanently in the database by means of the operation.
Union, Intersection as well as Difference
These are the normal set operators. The condition for executing any of these set operations is that the two (2) operand relations has to be union well-matched, i.e. they must have the identical ratio of the columns or attributes, for an instance let assume N and the ith column or attribute of every single table or relation (i = l,…, n) should be from the similar domain, they may not have the identical column or attribute names.
The UNION operator creates a table or relation which is comprised of every single row or tuple from both the stated tables or relations.
The INTERSECT operator creates a table or relation which is comprised of every single matching row or tuple from both the stated tables or relations.
The DIFFERENCE operator builds a table or relation which is comprised of every single rows or tuples that are present in the first table or relation only, but not in the second table or relation.
These three (3) operators can be symbolized diagrammatically as shown below.
Division
In its simplest method, this particular operation has a binary relation of R (Table – 1 , Table – 2) as the dividend as well as a divisor which has Table – 2. The result is a set, say, X, of data from Table – 1 such that Table – 1 € X if there is a row or tuple (Table – 1 , Table – 2) in R for every single Table – 2, that is the divisor value.
A Relational Database Management Systems (RDBMS)
The Oracle database is a Relational Database System (RDBMS) from Oracle Corporation which is getting broadly used in products as well as internet based systems over diverse platforms. Oracle database was industrialized by Larry Ellison, together with friends as well as the former coworkers Bob Miner plus Ed Oates; they had started a consultancy firm known as Software Development Laboratories (SDL). They termed their completed product as Oracle, after the code name of a CIA funded project they had worked on a prior employer, Ampex.
Oracle database, features full Extensible Markup Language (XML) database functionality with Oracle Extensible Markup Language (XML) database, improvements to the innovative Oracle Real Application Clusters, as well as self – tuning in addition to self – management abilities to assist increase Database Administration (DBA) productivity and competence. Furthermore, the built in Online Transaction Processing (OLAP) functionality has been stretched as well as important improvements as well as optimizations have been made for the Windows in addition to Linux operating systems (OS). A number of of the Oracle database is as follows:
• Enterprise User Security (Password Centric Enterprise User Privacy) – Controlling end user accounts is very much time consuming as well as expensive activity in numerous organizations. For an instance, end users may misplace their specific passwords, alter the roles otherwise leave the company. Without appropriate user administration, the field is exposed for information ill use as well as information loss. By means of presenting password centric based verification, Oracle Advanced Security has upgraded the ease of practice as well as easy enterprise end user arrangement in addition to administration.
• Oracle Partitioning – Oracle Segregation, a possibility of Oracle Enterprise Edition, can improve the manageability, performance, as well as obtainability of a wide range of systems. Segregation lets relations or tables, indexes, as well as index – managed relations or tables to be split into smaller units, allowing these database objects to be handled as well as retrieved at an improved level of granularity.
• Oracle Universal Connectivity as well as Oracle Transparent Gateway – Oracle allows two (2) connectivity solutions to address the requirements of dissimilar information access. They are: Oracle Universal Connectivity as well as Oracle Transparent Gateways. These two (2) ways out made it conceivable to access any number of non – Oracle systems from an Oracle environment in a heterogeneously dispersed environment.
• Performance Development – Performance has been always a big matter with databases. The main developments have been the Parallel Server which Oracle now termed as Real Application Clusters as well as this permit application to practice clustered servers devoid of alteration.
• Security Improvements – As the number of end users increased as well as the geographical locations along with the types of end users turn out to be more miscellaneous, improved security as well as privacy features come to be vital.
This will be the last part of the article series “Relational Data Modeling for Database Systems”, hope the readers had got some valuable information through this series.
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