Databse Management 4 Flashcards
the process of creating a specific data model for a determined problem domain; is a iterative progressive process.
data modeling
is a characteristic of an entity. For example, a CUSTOMER entity would be described by attributes such as customer last name, customer first name, customer phone number, customer address, and customer credit limit. Attributes are the equivalent of fields in file systems.
An Attribute
is a person, place, thing, or event about which data will be collected and stored.
entity
is a brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization. Properly written business rules are used to define entities, attributes, relationships, and constraints.
A Business Rule
manages large amounts of data for complex manufacturing projects, and contains levels or segments. A segment is the equivalent of a file system’s record type. Within the hierarchy, a higher layer is perceived as the parent of the segment directly beneath it, which is called the child. The hierarchical model depicts a set of one-to-many (1:M) relationships between a parent and its children segments.
Heirarchical model
was created to represent complex data relationships more effectively than the hierarchical model, to improve database performance, and to impose a database standard. In the network model, the user perceives the network database as a collection of records in 1:M relationships.
The Network Model
is the conceptual organization of the entire database as viewed by the database administrator.
The Schema
defines the portion of the database “seen” by the application programs that actually produce the desired information from the data within the database.
Subschema
defines the environment in which data can be managed and is used to work with the data in the database.
A data manipulation language (DML)
enables the database administrator to define the schema components.
A schema data definition language (DDL)
