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Steps for ER to relational mapping.
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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.

3] Relationships:

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.
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