YEAR 1 WEEK 20 CO1 RDBMS
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State purpose of RDBMS
main purpose of Relational Database Managment System is to maintain data integrity. Means all rules and relationships between data consistent all times.
What are some DBMS features.
Command language allows you to create, delete and alter the database (data definition language or DDL) A way of documenting all internal structures that make up the database (data dictionary) Language to support the manipulation and processing of the data (data manipulation language) Ability to view database from different viewpoints according to requirement of user. Provide some level of security and access control to the data.
Define a data dictionary.
A file which contains descriptions of the data stored in tables in a database. Used by database managers and administrators (DBM and DBA) Provides metadata or information about data and how it is stored. Describes the structure and attributes of data items.
State some items a data dictionary may store.
Table name Field name Field data type Field length Field validation Keys Relationship Indexes Access rights
What is the purpose of Data Definition Language.
One use is creating a database from scratch. Used to write schema which describes data items to be stored and the relationships between them. Allows tables to be created and primary/foreign keys to be defined Also defines validation rules.
What is the purpose of data manipulation language?
Provides a mean of manipulating data in the database. To access query sort search data Store insert data Change update delete data