With example explain Second Normal form. UG— BCA— Unit Introduction To Schema Refinement,. It then. Relational Data Model In this model the data is organized into tables called relations. Flag for inappropriate content. For Later. Related titles. Web Programming Unit- i. Taxation Notes. A record is also called as a row of data is each individual entry that exists in a table. A column is a vertical entity in a table that contains all information associated with a specific field in a table.
It is very important to understand that a NULL value is different than a zero value or a field that contains spaces. A field with a NULL value is the one that has been left blank during a record creation. Constraints are the rules enforced on data columns on a table. These are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the database. Constraints can either be column level or table level.
Column level constraints are applied only to one column whereas, table level constraints are applied to the entire table. Database normalization is the process of efficiently organizing data in a database. Both these reasons are worthy goals as they reduce the amount of space a database consumes and ensures that data is logically stored. Normalization consists of a series of guidelines that help guide you in creating a good database structure.
Normalization guidelines are divided into normal forms; think of a form as the format or the way a database structure is laid out. The aim of normal forms is to organize the database structure, so that it complies with the rules of first normal form, then second normal form and finally the third normal form.
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