1] Strong Entity Set:
A strong entity set reduces to schema with same attributes.
If E is strong entity set with descriptive attributes $a_1. . . a_n$ This entity set will be represented as E with n distinct attributes.
2] Weak entity set:
- Schema is a combination of primary key from identifying strong entity set and attributes of weak entity set.
a] One to one.
- Extra attribute is added to either of entity set schema corresponding to entity set participating in relationships.
b] Many to one/one to many.
- Extra attribute is added to many side entity set with primary key of one side entity set as a foreign key constraint.
c] Many to may.
- A separate schema is created with primary keys of participating schema.
4] Multi valued attribute:
- A separate schema is created with multi valued attribute and primary key of entity of entity whose multi valued attribute.
5] Composite attribute:
- These attributes are flattered to its constituent attributes.
6] Derived attribute:
- These attributes are ignored as their values can be derived from other attributes.