mapublisher attribute table derived from permenant

#Mapublisher attribute table derived from permenant software#

The number of participating entities in a relationship defines the degree of the relationship.Ĭardinality defines the number of entities in one entity set, which can be associated with the number of entities of other set via relationship set. These attributes are called descriptive attributes. Like entities, a relationship too can have attributes. Here, Works_at and Enrolls are called relationships.Ī set of relationships of similar type is called a relationship set. For example, an employee works_at a department, a student enrolls in a course. The association among entities is called a relationship.

Primary Key: A primary key is one of the candidate keys chosen by the database designer to uniquely identify the entity set.

An entity set may have more than one candidate key.

Candidate Key: A minimal super key is called a candidate key.

Super Key: A set of attributes (one or more) that collectively identifies an entity in an entity set.

Key is an attribute or collection of attributes that uniquely identifies an entity among entity set.įor example, the roll_number of a student makes him/her identifiable among students. These attribute types can come together in a way like: For example, a person can have more than one phone number, email_address, etc.

Multi-value attribute: Multi-value attributes may contain more than one values.

Single-value attribute: Single-value attributes contain single value.

For another example, age can be derived from data_of_birth. For example, average_salary in a department should not be saved directly in the database, instead it can be derived.

Derived attribute: Derived attributes are the attributes that do not exist in the physical database, but their values are derived from other attributes present in the database.For example, a student’s complete name may have first_name and last_name. Composite attribute: Composite attributes are made of more than one simple attribute.For example, a student’s phone number is an atomic value of 10 digits. Simple attribute: Simple attributes are atomic values, which cannot be divided further.For example, a student’s name cannot be a numeric value. There exists a domain or range of values that can be assigned to attributes. For example, a student entity may have name, class, and age as attributes. AttributesĮntities are represented by means of their properties, called attributes. For example, a Students set may contain all the students of a school likewise a Teachers set may contain all the teachers of a school from all faculties. An entity set may contain entities with attribute sharing similar values. All these entities have some attributes or properties that give them their identity.Īn entity set is a collection of similar types of entities. For example, in a school database, students, teachers, classes, and courses offered can be considered as entities. EntityĪn entity can be a real-world object, either animate or inanimate, that can be easily identifiable.

#Mapublisher attribute table derived from permenant software#

The physical data design model involves translating the logical design of the database onto physical media using hardware resources and software systems such as database management systems (DBMS). It does not concern itself with how the data will be stored or where it will be stored physically. The logical model concentrates on the data requirements and the data to be stored independent of physical considerations.

The main objectives of database designing are to produce logical and physical designs models of the proposed database system. That meet the requirements of the users.Database Design is a collection of processes that facilitate the designing, development, implementation and maintenance of enterprise data management systems