📌 CBSE Class 12 MySQL Notes – Last-Minute Revision
Preparing for your CBSE Class 12 Computer Science board exam? Need a quick and effective revision for MySQL? You're in the right place! This page provides concise, exam-focused MySQL notes designed for last-minute preparation.
DATABASE MANAGEMENT SYSTEM
1.Database: A Database is an organized collection of data, it can be visualized as a container of information.
2.Database Management System: DBMS is a software package with computer programs that control the creation, maintenance, and use of a database. A database is a collection of data and DBMS allows different user application programs to concurrently access the same database.
Examples of DBMS – Oracle, MySQL, FoxPro, IBM DB2, Microsoft SQL Server, OpenOffice.org Base, and Microsoft Access.
Organization of Data: Data can be organized in two ways –
1. Flat File: Data is stored in a single table. This is usually suitable for less amount of data.
2. Relational: Data is stored in multiples tables which are linked by a common field. This is suitable for medium to large amount of data.
3.Database Servers: These are dedicated computer systems that hold the databases and run only the DBMS and related software. Databases are available on database servers and are usually accessed through a command line or Graphic User Interface tools [called Frontend].
4.Limitation and disadvantages:
- Data redundancy (Duplication of data)
- Data inconsistency
- Unshakable data
- Unstandardized data
- Insecure data
- Incorrect data
5.Advantages of Database:
5.1) Reduces Data Redundancy: Database reduces data redundancy. Database reduces Duplication of data, in fact, there is no chance to encounter duplicate data in a database.
5.2) Reduce data inconsistency: Multiple mismatching copies of same data is known as data inconsistency
5.3) Sharing of Data: The users of the database can share the data among themselves.
5.4) Data Integrity: Data integrity means that the data in the database is accurate and consistent.
5.5) Data Security: Database provides data security as only authorized users are allowed to access the database and their identities are authenticated by using a username and password.
5.6) Privacy: Only authorized users can access a database according to the database privacy constraints.
5.7) Backup and Recovery: DBMS automatically takes care of backup and recovery. In case of a crash or system failure, it gets restored to its previous condition.
6. Features of Database:
· The database has one or more tables.
· Each table has information about one type of item.
· Every table in a database has a key field that makes sure that there are unique values throughout the database.
7. Keys in a Database:
7.1 Primary Key: A primary key is a unique value that identifies a row in a table. Primary Key helps the database to quickly search for a record.Not null values.
7.2 Composite Primary Key: When a primary key constraint is applied on one or more columns then it is known as Composite Primary Key.
7.3 Foreign key: The foreign key identifies a column or set of columns in one (referencing) table that refers to a column or set of columns in another (referenced) table.
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