An entity relationship diagram is the basic design model for any database. It is the major deliverable for a conceptual database design. It is the logical organization of any data in the database and is usually made up of three components namely; entities, attributes and relationships. Entities are the major categories of data in the database and are usually represented by rectangles. Attributes are the characteristics of the entities and are usually written in the rectangle. Relationships are the connections between entities and are usually represented using lines joining the rectangles. Entities that share major characteristics are known as entity types, and are also referred to as classes. An entity instance is the individual occurrence of one entity type. It is important to define entity types as it makes it easier to determine the requirements of the database and how it will be structured.
In defining an attribute, the analyst must state the importance of the attribute, the value of the attribute and whether the value of this attribute can change. When drawing an entity relationship diagram, the analyst must be aware of the following types of attributes; multi-valued attributes, required attributes, optional attributes, composite attributes and derived attributes. When showing relationships, an analyst must be aware of three types of relationships; unary (between instances of one entity type), binary (between instances of two entity types), and ternary (between
The ERD represents conceptualization by end users of what the database has to offer. As a database designer, it is important for you to use the ERD tool so the components, attributes, entities and relationships are clearly visible. The ERD tool will held database designers make sure they are capturing all required data and that all tables needed are built around that data.
According to Kroenke and Auer (2010) there is an ERD standard, albeit very loosely practiced. The diagrams use combinations of rectangles and diamonds. Entity classes are shown using rectangles, relationships are shown using diamonds, the maximum cardinality of the relationship is shown inside the diamond, and the minimum cardinality is shown by the oval or hash mark next to the entity. The name of the entity is shown inside the rectangle and the name of the relationship is shown near the diamond.
Business Rules: In the entity-relationship data models, business rules must take into account all relationship models: one-to-many (1:M), one-to-one (1:1) and many-to-many (M:N). For a database on a school library, a restriction of having a student only allowed to borrow one book would need a 1:1 relationship.
2. using the data requirements and the business rules provided, develop a conceptual model (ERD), including attribute data types and required field lengths; and
A relational database is a database that consists of a collection of tables with columns showing entities, and rows showing data. This type of database uses a primary key and foreign key. The foreign key in another table will point to the primary key of a table, and this is how tables can relate to each other. This permits for one-to-one, one-to-many, and many-to-many relationship between the data. An advantage of relational databases includes the ease of adding or modifying new tables and entities without needing to change the structure of the database already in place. Relational database have many features, including indexing, setting data type, and setting validation tests, all these help to ensure data integrity.
Draw an REA diagram with cardinalities and tables with primary keys, foreign keys, and non-key attributes for the following business:
When it comes to the data model, there exists a relationship that has three different representations for the reason that database requires the relationship between the tables. It goes hand-in-hand with one another without the relationship the tables would have no purpose. The information cannot be repetitive in order for the each table to work and provide the specific database that is related to the information. In different ways the tables in the Huffman Trucking Fleet Truck database
* As explained throughout this course, entity relationship modeling is a critical element of database design. If the database is not properly modeled, it is unlikely that the database will be properly developed. Using this knowledge, explain the key reasons why entity relationship modeling is important, and determine at least (1) way in which it impacts the overall development of the database.
Which of the following defines a relationship in which each occurrence of data in one entity
Example 1 – Consider the following relational database for the Super Baseball League. It keeps track of teams in the league, coaches and players on the teams, work experience of the coaches, bats belonging to each team, and which players have played on which teams. Note the following facts about this environment:
During first period I observed Dana Bealing’s AP Calculus class. At the beginning of class Dana handed out the materials for the day. This included a project handout, a notes worksheet for the day’s lesson, and an example worksheet. During this time Dana connected with students by asking them how they dealt with the snow. She asked the students if they had any wild blizzard stories from the weekend. Dana announced to the students that there were going to be changes to the assignments due to the snow. She also took this time to tell the students that they needed to complete the final exam revisions if they had not already done so. These papers were handed to the students as they were walking in the classroom. The next activity included a
Danniel Moreno Reform Movements expanded Democratic ideals Reform movements and awakenings has been starting to appear during the mid 1800’s. Many of these movements help improved society and better change in equality roles. The reform movements has been created by the people to change the Nation to have ideals turn into society communities. In addition, reform movements helped expand democratic ideals as society and rights between people, were improving and changing. Reform movements have sought to expand democratic ideals by religion revivals, social equality, and organization.
Rape of Dinah- Genesis 34:1-34 The rape of Dinah occurs when Dinah went out to the town of Shechem to go meet another young woman. When she arrives, she is raped by a man named Shechem, who is son of the town’s chief, Hamor. Shechem then decides that he wants to marry Dinah. Dinah’s brothers tell Shechem that in order to marry Dinah, all of the men in the city must be circumcised. Dinah’s brothers, Simeon and Levi, then go into the city and murder Shechem and Hamor, and rescue Dinah.