CBSE Class 12 Informatic Practices MySQL

Database Concepts

After studying this lesson the students will be able to: 

   Recall the terminology used in RDBMS concepts. 

   Recall and effectively use the SQL commands and clauses learnt in class XI. Realize that much more is to be learnt for effective use of databases. 

In the previous class, you have learnt some database concepts and SQL commands. You have also learnt how to access data from a table using various clauses of SELECT command. In this lesson we are going to revise the database concepts and SQL studied in class XI. That will make the base for further reading of the concepts and some more SQL commands which are really very useful in practical applications.

You have already studied the following database concepts in class XI:

1. Database: A database is an organised collection of data. Software used to manage databases is called Data Base Management System (DBMS).

2. Relational Database: A database in which the data is stored in the form of relations (also called tables) is called a Relational Database. In other words a Relational Database is a collection of one or more tables.

3. RDBMS: A DBMS used to manage Relational Databases is called an RDBMS (Relational Data Base Management System). Some popular RDBMS software available are: Oracle, MySQL, Sybase, Ingress MySQL - REVISION TOUR

4. Benefits of using a DBMS are:

   a. Redundancy can be controlled

   b. Inconsistence can be avoided

   c. Data can be shared

   d. Security restrictions can be applied.

5. MySQL: It is an Open Source RDBMS Software. It is available free of cost.

6. Relation/Table: A table refers to a two dimensional representation of data arranged in columns (also called fields or attributes) and rows (also called records or tuples). The tables in a database are generally related to each other to facilitate efficient management of the database. Interrelated tables also reduce the chances of errors in the database.

7. Key: A column or a combination of columns which can be used to identify one or more rows (tuples) in a table is called a key of the table.

8. Primary Key: The group of one or more columns used to uniquely identify each row of a relation is called its Primary Key.

9. Candidate Key: A column or a group of columns which can be used as the primary key of a relation is called a candidate key because it is one of the candidates available to be the primary key of the relation 

10. Alternate Key: A candidate key of a table which is not made its primary key is called its Alternate Key.

Let us now revise MySQL concepts studied in class XI with the help of a Library database.

Note: As this is a revision lesson, all variations of SQL commands are not covered here. It is suggested that they are revised through practical assignments. Think of the functioning of a computerised school library. In a school library, there are books which are issued to the students and the staff. These books are also returned after a certain period of time. For proper functioning of this system the librarian maintains a database (an organised collection of data) which contains the relevant data of books, students, and staff. In a relational database, this data may be organised as a collection of the following tables:

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