ERD

Overall design -> Schema
->
Entity Relatuonship Model

Schema is two types :

1. Physical Schema
2. Logical Schema Level -> 1. View
3. Logical Level
4. Physical Level

Instance ->
Particular data combination of row and column in a partucular time

Each row represents entity or record or content

Data Model :
Entity Relationship Diagram
Basic Needs :

1. Domain
2. Sub Domain
3. Cross point
4. Attribute
5. Relationship
6. Constraints SDLC have 6 steps :
7. Physibility study : Requirement Analysis : 6 step is requirement analysis
8. User Requirement
9. System Requirement Entity -> Important data of the software একটা সিস্টেম কে পরিপূর্ণতা দেওয়ার জন্য যেই data রাখা important is called entity Attribute : Characteristics of entity. Entities are represented in the form of table. Single Valued Multiple Valued. Composite-> To form a attribute if another attribute is needed. Derived -> Key Non key Stored Derived -> Comes from another attribute. Grand pa -> Dad -> Me

Multi valued -> phone number more than one
Entity set -> A group of student with same characteristics data

Prime Attribute ->
Primary key->