Database Knowledge Reserve-(i)

1. Three main paradigms:

The first paradigm (1NF) is that each column of a database table is an indivisible base data item and cannot have multiple values in the same column, that is, an attribute in an entity cannot have multiple values or cannot have duplicate properties.

Second Normal form (2NF): requires that each instance or row in a database table must be divided by a unique region.

Third paradigm (3NF): Requires that a database table not contain non-primary key information already contained in other tables.

2.

• Two tiers C/S: Client-Server (logic processing is all in the client, known as ' Fat client ')
• Three layer C/S: Client-Application Server-database server (logic processing on application server)
• b/S mode (three layer C/s special form): Browser-web Server-database server (Web server handles HTTP requests by responding to HTML pages)

Database Knowledge Reserve-(i)