Database Courses ? 2 (Entity ? Relationship Model )
ENTITY ? RELATIONSHIP MODEL (E-R Diagram)
Entity ? Relationship model is a Database design tool for creating a diagram.
( ?entity? means record, object )
? Binary Relationship Set
? Ternary Relationship Set
There are kinds of attributes. Some of them is like that:
? Single valued attribute: at most one value
For example; firstname, lastname..
?Multi-valued attribute: 0 or more similar values. We don?t put them to the E-R diagram, but we can draw another table for it.(with primary key of the table which it belongs to)
Such as phone number, e-mail, address
?Derived attribute: It is derived from another attribute
For example, age is a derived attribute. It can not be stored. It changes and it is derived from birthdate. We don?t put them to the E-R diagram.
See you soon..
Yoruma Açığız! :)