How to decide whether to use ER or UML for modelling?

Question

A UML diagram can be used both to model database designs and class designs, but an ER diagram should be used exclusively in database problems. How do you pick one graphical representation over the other?

Answer 1

ERD - Entity Relation Diagram - giving you image of how the tables should connect, what fields are going to be on each table, the tables connection, if many-to-many, one-to-many.

UML can be used for many diagrams other then ERD. sequence diagram, state diagram, more for the funcionality of the application (what user can do, who does it, when he does it, before what step, what table he use to do it) other then the tables description.

I Would use ERD to describe database relation and UML to describe operations, time, actions, etc..

Refer wiki : Entity-relationship_diagram & Unified_Modeling_Language

Answer 2

Just use always UML since it kind of subsumes ER. The only reason to use ER would be if you´re using a tool (e.g. to generate the DDL SQL scripts to create the tables) that only supports ER (now most do support UML but you may still find some that sticked to ER)

Answer 3

UML is the notation so if you are speaking with people who understand UML it would be beneficial to use UML. A classical entity relationship diagram is usually in Chen notation.

Personally I have found that I always use UML for modeling entity relationships and only used Chen in academia.