RELATIONAL DATABASE MANAGEMENT SYSTEM
SQL (short for structured query language) is an industry-standard language specifically designed to enable people to create databases, add new data to databases, maintain the data, and retrieve selected parts of the data.
Various kinds of databases exist, each adhering to a different
conceptual model.
SQL was originally developed to operate on data in databases that follow the relational model.
Recently, the international SQL standard has incorporated part of the object model, resulting in hybrid structures called object-relational databases. In this Blog, I discuss data storage, devote a section to how the relational model compares with other major models, and provide a look at the important features of relational databases.
Before I talk about SQL, however, first things first:
I need to nail down what I mean by the term database. Its meaning has changed as computers have changed the way people record and maintain information.
What Is a Database:
The term database has fallen into loose use lately, losing much of its original meaning. To some people, a database is any collection of data items (phone books, laundry lists, parchment scrolls . . . whatever).
Other people define the term more strictly.
A database as a self-describing collection of integrated records. And yes, that does imply computer technology, complete with languages such as SQL.
example, that you want to keep track business’s customers.
You assign a record for each customer. Each record has multiple attributes, such as name,address, and telephone number. Individual names, addresses, and so on are the data.
A database consists of both data and metadata. Meta data is the data that describes the data’s structure within a database. If you know how your data is arranged, then you can retrieve it. Because the database contains a description of its own structure, it’s self-describing. The database is integrated because it includes not only data items but also the relationships among data items.
The database stores meta data in an area called the data dictionary, which describes the tables, columns, indexes, constraints, and other items that make up the database.
DBMS:
DBMS means Database Management System.
What Is a Database Management System:
A Database management system (DBMS) is a set of programs used to define,administer, and process databases and their associated applications.
The database being “managed” is, in essence, a structure that you build to hold valuable data. A DBMS is the tool you use to build that structure and operate on the data contained within the database.
Many DBMS programs are on the market today. Some run only on mainframe computers, some only on minicomputers, and some only on personal computers.
A strong trend, however, is for such products to work on multiple platforms or on networks that contain all three classes of machines.
A DBMS that runs on platforms of multiple classes, large and small, is called scalable.
Whatever the size of the computer that hosts the database and regardless of whether the machine is connected to a network the flow of information between database and user is the same.
In the below figure shows that the user communicates with the database through the DBMS. The DBMS masks the physical details of the database storage so that the application need only concern itself with the logical characteristics of the data, not how the data is stored.
Advantages of Database Management System:
1. Allows remote login.
2.Eases the problem for mobility because of number1(remote login)
3.Allows sharing of research and other works.eg like we are doing
now(sharing)
4.Makes it for the database administrator to monitor user
activities.
5.Provides necessary security to protect the data stored.
RDBMS:
A relational database management system (RDBMS) is a database
management system
(DBMS) that is based on the relational model as introduced by E.
F. Codd.
Most popular commercial and open source databases currently in use
are based on the
relational model.
A short definition of an RDBMS may be a DBMS in which
data is stored in the form of tables and the relationship among
the data
is also stored in the form of tables.
Advantages of RDBMS:
Consistency:
Data is guarantees to be consistent. Irrespective of the number of Custom Web Design simultaneously accessing it. An RDBMS always implements suitable locking mechanisms to prevent data inconsistency. A transaction either goes through fully or not at all i.e. it is either “committed “or “rolled back”.
Recoverability:
Irrespective of the type of failure, it is always possible to
recover the data base upto
the most recent consistent state. This means that if recovery measures are correctly implemented you would not lose all days work. And thus no need to reenter.
Distributability:
Database can be distributed in more than one physical location. Irrespective of this, application’s view of the database remains same as though it is in a single location. Applications need not undergo any change if the distribution of the data changes.
Support for IV generation
languages: (4GL):
RDBMS support 4GL. Today, there is even a standard 4GL in the structured query Language (SQL) form. The main difference between 4GLs and 3GLs is that in the former the user needs to specify what is required and not how it has to be done.
Transaction rules:
Rules, processes and constraints can be integral part of the data
bases. This ensures that all transactions must obey these rules if they are to
be successful. This offers a single point control.
Database:
A database is a collection of information that is organized so that it can easily be accessed, managed, and updated.
