Management information systems is a multidisciplinary field that involves the study of people. Management System (HDMS) for Medical Doctors. Amaechi James C., Agbasonu Valerian C., and Nwawudu Sixtus E. International Journal of Computer Theory and Engineering, Vol.
Er Diagram For College Management System Download What IsEntities , defined as tables that hold specific information (data) ER models are readily translated to relations. ER models, also called an ER schema, are represented by ER diagrams. It is well suited to data modelling for use with databases because it is fairly abstract and is easy to discuss and explain. Chapter 8 The Entity Relationship Data ModelThe entity relationship (ER) data model has existed for over 35 years. According to this notation, the entity is represented by rectangle, relation is depicted by line which ties two entities involved in a relationship. Entity-relationship diagrams based on both Abstract for college management system best college management system college event management system college library management system er diagram college management system abstract college management system application college management system case study college management system codecanyon college management system database tables college management system demo college management system diagram college management system er diagram college management system github college management system images college management system in php college management system java project college management system java project netbeans college management system login college management system logo college management system malaysia college management system modules pdf college management system project in c language college management system project in java github college management system project in php college management system project in python college management system project in vb.net with documentation college management system project modules college management system project report in java college management system project report in php college management system report college management system sql queries college management system synopsis college management system template college management system uml diagrams college management system use case diagram college management system web application college management system website college management system wordpress plugin introduction of college management system ksrct college management system modules in college management system objective of college management system odoo college management system online college management system scope of college management system skidmore college housing management system srs for college management system srs for college management system download what is college management system what is university management systemThis is the UML sequence diagram of College Management System which shows the interaction between the objects of Students, Login, College, Branches, Faculties.There are several departments in the company. Important points to note include: This database contains information about employees, departments and projects. Ba (entity) teaches (relationship) the Database Systems course (entity).For the rest of this chapter, we will use a sample database called the COMPANY database to illustrate the concepts of the ER model.We want to keep track of the dependents for each employee. We also need to know the direct supervisor of each employee. We need to record the start date of the employee in each project. An employee is assigned to one department but can join in several projects. Each employee has a name, identification number, address, salary and birthdate. A department controls a number of projects, each of which has a unique name, a unique number and a budget.
That is, it cannot exist without a relationship with another entity An entity is considered weak if its tables are existence dependent. An object with conceptual existence (e.g., a course, a job, a position)Entities can be classified based on their strength. An object with physical existence (e.g., a lecturer, a student, a car) ERD with entity type EMPLOYEE. For example, in Figure 8.1, the entity type is EMPLOYEE. In an entity relationship diagram (ERD), an entity type is represented by a name in a box. A table without a foreign key or a table that contains a foreign key that can contain nulls is a strong entityAnother term to know is entity type which defines a collection of similar entities.An entity set is a collection of entities of an entity type at a particular point of time. Without a corresponding employee record, the spouse record would not exist.An entity is considered strong if it can exist apart from all of its related entities. The Spouse table, in the COMPANY database, is a weak entity because its primary key is dependent on the Employee table. Luffy new bountyThese are described below. Kinds of EntitiesYou should also be familiar with different kinds of entities including independent entities, dependent entities and characteristic entities. For example, in the COMPANY database, a Spouse entity is existence -dependent on the Employee entity. It is existence-dependent if it has a mandatory foreign key (i.e., a foreign key attribute that cannot be null). The foreign key identifies each associated table. Many to many relationships become associative tables with at least two foreign keys. They are said to be existence dependent on two or more tables. Dependent entities are used to connect two kernels together. They typically have a one to many relationship. These entities have the following characteristics: Use a composite of foreign keys and a qualifying columnCharacteristic entities provide more information about another table. Use a composite of foreign keys of associated tables if unique Er Diagram For College Management System Plus A QualifyingIn the COMPANY database, these might include: Create a new simple primary key. Use a composite of foreign key plus a qualifying column Options for primary key are as follows: How attributes are represented in an ERD. However, the information about attribute domain is not presented on the ERD.In the entity relationship diagram, shown in Figure 8.2, each attribute is represented by an oval with a name inside. Here, EID is also a foreign key.Each entity is described by a set of attributes (e.g., Employee = (Name, Address, Birthdate (Age), Salary).Each attribute has a name, and is associated with an entity and a domain of legal values. EmployeePhone ( EID, Phone) – EID is part of a composite primary key. An example of composite attributes. In the COMPANY database, an example of this would be: Name = Figure 8.3. Simple attributesSimple attributes are those drawn from the atomic value domains they are also called single-valued attributes. Later on we will discuss fixing the attributes to fit correctly into the relational model. This first section will discuss the types of attributes. Some of these are to be left as is, but some need to be adjusted to facilitate representation in the relational model. Derived attributesDerived attributes are attributes that contain values calculated from other attributes. Example of a multivalued attribute. An example of a multivalued attribute from the COMPANY database, as seen in Figure 8.4, are the degrees of an employee: BSc, MIT, PhD. Types of KeysThere are several types of keys. The key is an attribute or a group of attributes whose values can be used to uniquely identify an individual entity in an entity set. KeysAn important constraint on an entity is the key. Example of a derived attribute. In this situation, Birthdate is called a stored attribute, which is physically saved to the database. Age can be derived from the attribute Birthdate. Last Name and Department ID – assuming two people with the same last name don’t work in the same departmentThe primary key is a candidate key that is selected by the database designer to be used as an identifying mechanism for the whole entity set. Last Name and DepartmentID – assuming two people with the same last name don’t work in the same departmentA composite key is composed of two or more attributes, but it must be minimal.Using the example from the candidate key section, possible composite keys are: First Name and Last Name – assuming there is no one else in the company with the same name It is minimal because every column is necessary in order to attain uniqueness.From our COMPANY database example, if the entity is Employee(EID, First Name, Last Name, SIN, Address, Phone, BirthDate, Salary, DepartmentID), possible candidate keys are: It is unique because no two rows in a table may have the same value at any time. Candidate keyA candidate key is a simple or composite key that is unique and minimal. This is referred to as the primary key. A key is chosen by the database designer to be used as an identifying mechanism for the whole entity set. A candidate key is selected by the designer to uniquely identify tuples in a table. The primary key is indicated in the ER model by underlining the attribute. Free printable generic lease agreementBoth foreign and primary keys must be of the same data type. Foreign keyA foreign key (FK) is an attribute in a table that references the primary key in another table OR it can be null. Alternate keyAlternate keys are all candidate keys not chosen as the primary key.
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