This document discusses data models and their components. A data model includes entities, attributes, data values, key attributes, and records. Entities represent people, places, things, events or concepts, attributes characterize entities and describe them meaningfully, data values are the attribute values, key attributes uniquely identify records, and records are collections of entity attributes. Relationships between entities can be one-to-one, one-to-many, or many-to-many. Common symbols are used in entity-relationship diagrams to represent these components and relationships.

1. DATA MODELS

2. Relationships within a data model Entity AttributesData ValueKey AttributesRecord

3. EntityPerson,place,thing,event or concept about which the information is recorded AttributesAttributes characterise the entity or describe the entity meaningfully. Data Value Each attribute of an entity has a value and is called as data value

4. Key AttributesThe key attributes are used to find the values of other attributes RecordRecord is the collection of the attributes of an entity

5. Relation types ONE- TO- ONE ONE – TO- MANY MANY - TO- MANY

6. Symbols used in E-R DiagramONE RELATION ENTITYRELATIONMANY RELATION

7. occupiesONE-TO-ONEpatientbedassignedONE TO ONE RELATION

8. HOSPITALROOMPATIENTONE-T0-MANYACCOMADATESONE-TO-MANY RELATION

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