Construction of a Relational Database Using an EER Model
constructing of Relational Database using an EER Model
4.1 The steps involved in the design of relational database are
1) Developing the conceptual model – Drawing the ER/ EER diagram 2) Transforming the Conceptual model into a set of relations – relational schema and 3) Normalizing the relations.
Once ER / EER model has been developed for the application , ER/ EER diagram can be mapped into a relational model .
ER/ EER diagram consists of the following components. 1) Entities (Strong , Weak) with attributes 2) Attributes may be Single, Simple, composite or multi valued attributes 3) Relationships with cardinality ratios (1:1, 1:N, N: M) 4) Ternary relationship 5) In the case of EER diagram, concept of generalization, categorization and aggregation
4.2 Translation of EER diagram into a set of relations includes the translation of 1) Strong Entity 2) Weak Entity 3) Multi valued attributes 4) Unary relationship 5) Binary relationships (1:1 and 1:M) 6) M: N relationships 7) Ternary relationship 8) Associative entity 9) Generalization / Specialization 10) Categorization (union) and 11) Aggregation
The transformation includes the translation of all the above components in the following steps 4.2.1 Translation of Entity Strong Entity : Each strong entity in the ER / EER diagram will be a relation on translation. The attributes of the entities will be automatically the attributes of the relation. One of the attributes which has unique and single value will be the primary key of the relation. Weak Entity: Each weak entity will also be translated into a relation. The attributes will be the attributes of the relation By definition the existence of weak entity depends upon the other strong entity. Known as Owner entity This characteristic is reflected in fixing the primary key of the relation corresponding to the weak entity. The primary key will be a
4.1 The steps involved in the design of relational database are
1) Developing the conceptual model – Drawing the ER/ EER diagram 2) Transforming the Conceptual model into a set of relations – relational schema and 3) Normalizing the relations.
Once ER / EER model has been developed for the application , ER/ EER diagram can be mapped into a relational model .
ER/ EER diagram consists of the following components. 1) Entities (Strong , Weak) with attributes 2) Attributes may be Single, Simple, composite or multi valued attributes 3) Relationships with cardinality ratios (1:1, 1:N, N: M) 4) Ternary relationship 5) In the case of EER diagram, concept of generalization, categorization and aggregation
4.2 Translation of EER diagram into a set of relations includes the translation of 1) Strong Entity 2) Weak Entity 3) Multi valued attributes 4) Unary relationship 5) Binary relationships (1:1 and 1:M) 6) M: N relationships 7) Ternary relationship 8) Associative entity 9) Generalization / Specialization 10) Categorization (union) and 11) Aggregation
The transformation includes the translation of all the above components in the following steps 4.2.1 Translation of Entity Strong Entity : Each strong entity in the ER / EER diagram will be a relation on translation. The attributes of the entities will be automatically the attributes of the relation. One of the attributes which has unique and single value will be the primary key of the relation. Weak Entity: Each weak entity will also be translated into a relation. The attributes will be the attributes of the relation By definition the existence of weak entity depends upon the other strong entity. Known as Owner entity This characteristic is reflected in fixing the primary key of the relation corresponding to the weak entity. The primary key will be a