Monday, 20 November 2017

DBMS basic terminology and concepts




Basic Concepts:
Data is organized in a data storage hierarchy of increasingly complex levels: bits, bytes (characters), fields, records, files, and databases. A character is a letter, number, or special character. A field consists of one or more characters (bytes). A record is a collection of related fields. A file is a collection of related records. A database is, as mentioned, an organized collection of integrated files. Important to data organization is the key field, a field used to uniquely identify a record so that it can be easily retrieved and processed.



Introduction to database

Every one deals with data every day. When anyone wants to listen to his/her favorite songs, he opens his playlist from the smartphone. In this case, the playlist is a database.

When you take a photo and upload it to your account in a social network like Facebook, your photo gallery is a database.

Databases are everywhere. So what is a database?  By definition, a database is simply a structured collection of data or you can say – a collection of information.

The data relates to each other by nature e.g., a product belongs to a product category and associated with multiple tags. This is why we use the term relational database. In the relational database, we model data like products, categories, tags, etc., using tables. A table contains columns and rows. It is like a spreadsheet.
A table may relate to another table using a relationship e.g., one-to-one and one-to-many relationships.
Because we deal with a large amount of data, we need a way to define the databases, tables, etc., and process data more effectively. In addition, we want to turn the data into information.


 SQL

SQL – the language of database SQL stands for structured query language. SQL is the standardized language used to access the database.
ANSI/SQL defines the SQL standard. The current version of SQL is SQL:2003. Whenever we refer to the SQL standard, we mean the current SQL version.



SQL contains three parts:


  1. ·         Data definition language contains statements that help you define the database and its objects e.g., tables, views, triggers, stored procedures, etc.
  2. ·         Data manipulation language contains statements that allow you to update and query data.
  3. ·         Data control language allows you to grant the permissions to a user to access a certain data in the database.


 MySQL

MySQL is an open source relational database management system (RDBMS) based on Structured Query Language (SQL). It is used to manage the relational database by exploiting SQL. Its name is a combination of "My", the name of co-founder Michael Widenius's daughter,[8] and "SQL", the abbreviation for Structured Query Language. MySQL is a database management system that allows you to manage relational databases. It is open source software backed by Oracle. It means you can use MySQL without paying a dime. In addition, if you want, you can change its source code to suit your needs. MySQL is pretty easy to master in comparison with other database software like Oracle Database, or Microsoft SQL Server. MySQL can run on various platforms UNIX, Linux, Windows, etc. You can install it in a server or even in a desktop. In addition, MySQL is reliable, scalable, and fast.





RDBMS

A Relational Database management System(RDBMS) is a database management system based on relational model introduced by E.F Codd. In relational model, data is represented in terms of tuples(rows).

RDBMS is used to manage Relational database. Relational database is a collection of organized set of tables from which data can be accessed easily. Relational Database is most commonly used database. It consists of number of tables and each table has its own primary key.

What is Table ?

 In Relational database, a table is a collection of data elements organised in terms of rows and columns. A table is also considered as convenient representation of relations. But a table can have duplicate tuples while a true relation cannot have duplicate tuples. Table is the most simplest form of data storage. Below is an example of Employee table.

ID            Name    Age        Salary
1              Adam    34           13000
2              Alex       28           15000
3              Stuart    20           18000
4              Ross       42           19020

What is a Record ?

A single entry in a table is called a Record or Row. A Record in a table represents set of related data. For example, the above Employee table has 4 records. Following is an example of single record.

1              Adam    34           13000

What is Field ? 

A table consists of several records(row), each record can be broken into several smaller entities known as Fields. The above Employee table consist of four fields, ID, Name, Age and Salary.

What is a Column ? 

In Relational table, a column is a set of value of a particular type. The term Attribute is also used to represent a column. For example, in Employee table, Name is a column that represent names of employee.

Name
Adam
Alex
Stuart
Ross



Practice questions

What is the difference between MySQL and SQL?

SQL stands for Structured Query Language. It's a standard language for accessing and manipulating databases. MySQL is a database management system, like SQL Server, Oracle, Informix, Postgres, etc. MySQL is a RDMS (Relational Database Management System).

What is the difference between Database and DBMS?

Generally if  anyone asked about the difference between Database and DBMS then everyone says that both are same but there is huge difference between them are as:-

1.Both are part of the Database system.
3.Databse contains
      a) Data
      b)schema(structure of the table ).
2.DBMS contains
        a) Query Processing software.
        b)storage Management software.
    Examples :-MySQL, MS SQL Server, Oracle



4.Both are interdependent.

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