DB Sys WK 7 Peer Res Download The Attachment and Message Me Please for Detailed Instructions Discussion Post 1 The entity-relationship model is a high-lev

DB Sys WK 7 Peer Res Download The Attachment and Message Me Please for Detailed Instructions Discussion Post 1

The entity-relationship model is a high-lev

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Discussion Post 1

The entity-relationship model is a high-level data model developed using a collection of entities or objects and their relationships. Entity-relationship models show a conceptual view of a database and its components, relationships, and attributes that makeup entity sets, relationship sets, and attribute sets. The relational model is a model for representing data and the relationships between that data in tables. In the case of a relational model, these tables are called relations. According to Mohapatra (2019), the correspondence between ER model and the relational model is that both models are types of data models that are useful for describing database design at different levels. They define a database`s physical, logical, and view levels and show its relationships. Although an entity-relationship model offers a more straightforward relationship than a relational model, which uses tables, they convey information relating to the database structure. It is possible to map an entity-relationship model to a relational model construct.

Because the mapping in the entity-relationship model describes mapping maps while the mapping in the relational model does not, it is important to learn how to convert the entity-relationship model structure to the entity-relationship model structure. relational model architecture. To start converting an entity-relationship model to a relational model, create a diagram for the entity-relationship model and convert it to the relational model. Map these entities as relationships in a relation schema, for the entity attributes, map them to the relationship, and restore the entity’s primary attributes to be the primary key for the relationship. certain relationship (Ketan, 2020). Create tables for different entities and enter their attributes, specify applicable constraints like data types, make sure to declare the primary key. For all relationships in the database, create relational tables and add the corresponding primary keys and data types to them. Convert these relationships to tables and use different graphs, depending on whether the database entity set is single or multiple value sets.

References

Ketan Patil. (2020, September 27th). ER Diagram to Relational Model Conversion. https://dev.to/ketan_patil/er-diagram-to-relational-model-conversion-49ip

Mohapatra, Hitesh. (2019). DATABASE SYSTEM Entity-relationship model, Components of ER model, Mapping E-R model to Relational schema, Network and Object-Oriented. 10.13140/RG.2.2.12807.65449.

https://www.researchgate.net/publication/332170707_DATABASE_SYSTEM_Entity_relationship_model_Components_of_ER_model_Mapping_E-R_model_to_Relational_schema_Network_and_Object_Oriented

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Discussion Post 2

Discuss the correspondences between the ER model constructs and the relational model constructs. Show how each ER model construct can be mapped to the relational model, and discuss any alternative mappings?

In ER model collection of entities and relations between them are expressed. In the relational model, relations are expressed through tables. A relational model is a collection of data and relation between the data that is represented in the form of tables. An ER model contains a 1:N relation type whereas relational model foreign keys are used. In the relational model, relationship types are not explicitly specified. They are related using Primary and Foreign keys belonging to two tables or relations. A single join operation is needed when 1:1 or 1:N and Foreign key mapping is used. A two join operation is used when M: N-type and relationship relation are used. Separate relation is created for a multivalued attribute in a relation schema (Elmasri & Navathe, 2015). Each entity in an ER model is mapped to a table in the relational model and attributes are represented as fields in a table. Next, the weak entity is mapped by the primary key of identified entity set can be added and foreign keys are declared. A weak entity does not associate with any primary key. Next mapping is related to hierarchical entities. To map this to the relational model, create a table of higher-level entities and lower entities. Primary keys of higher-level are added to lower-level entities. Finally, declare the constraints of foreign keys (Tutorialspoint, 2019).

References

Elmasri, R., & Navathe, S. (2015). Fundamentals of Database Systems. Pearson.

Tutorialspoint. (2019). ER model to relational model. Retrieved February 17, 2022, from https://www.tutorialspoint.com/dbms/er_model_to_relational_model.htm

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Discussion Post 3

Correspondence between ER Model and Relational Model Constructs

We can define ER models as a collection of entities, while a relational model consists of data and relations among those data defined in tables (Chan, 1998). Entity relations in a relational schema are relations created from mapping entity types in the ER schema. In an ER model, you cannot explicitly represent relationship types compared to a relational model. Mapping of ER model construct to a relational model starts with mapping any strong entity type with; a primary key is selected from one of the key attributes or it can be a composite of simple attributes together. We then go on to map the weak entity types with the owner entity type, including defining foreign keys by the primary key attributes of the owner entity. In this way, we map the identifying relationships of the weak entity. The primary key of this entity relation is a combination of the primary key of its owner and the partial key of the weak entity type (Elmasri & Navathe, 2016).

Mapping of binary 1:1 relationship types takes place by identifying the relations that correspond to the entity types participating in this relationship type. We can do this by: (1) including a foreign key in one relation as the primary key of the other, (2) Merging two entity types and their relationship into a single relation, or (3) Create a relationship relation by setting up a third relation. Mapping of binary 1: N relationship types is similar except in this case there are only two approaches: (1) foreign key approach, (2) Cross-reference or relationship-relation type approach. For mapping of binary M: N and N-ary relationship types, there is only one approach – the relationship relation type (Elmasri & Navathe, 2016).

References

Elmasri, R. & Navathe, S. B. (2016). Relational Database Design by ER- and EER-to-Relational Mapping. In Fundamentals of Database Systems (7th ed., pp. 289–306). Pearson Company.

Chan, H. C. (1998). User performance differences between relational and entity relationship models: a summary review of the literature. Behaviour & Information Technology, 17(1), 59–61. https://doi.org/10.1080/014492998119689

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