Data is some piece of information that should be stored for future manipulations. The system which provides such a facility is called Database Management System or DBMS.
Data for future purpose can be saved in either a text file or excel sheet or in some other place.
Data for future purpose can be saved in either a text file or excel sheet or in some other place.
The simplest form to store a data for later retrieval is using a text file.
Example : you may want to store your friends name and phone numbers to use it latter.This kind of storage is called flat file storage or unstructured storage.
But ,flat files are not suitable to large data such as storing employee details in an organization. To overcome this we need some system which should perform the storing,retrieving, manipulating and querying operations on the data and give output to us. This kind of system is called Database Management System.
DBMS : Database Management System which organizes and stores data in a structural way for fast retrieval and for data manipulations.
Some of the well known Database Management Systems are Microsoft SQL Server, Sybase, Oracle, IBM DB2, PostgreSQL, MySQL and SQLite.
Every DBMS has it is own language to write the commands. All database queries are standardized under a common language called Structured Query Language(SQL). SQL is a language used to storing,retrieving, manipulating data in a relational database.SQL also contains statements for defining and administering the objects in a database. SQL is the language supported by most relational databases.
All most all the databases store information in tables. Some of the frequently used terms in SQL are:
Column – A finite unit of data. It is represented by one of the data type.
Row – A collection of Columns.
Tables – Collection of rows.
Database – Collection of tables and other objects. 
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