MIS Chapter 5 Review
Identifier/Primary Key
→ Every record in an entity must be uniquely identified (Primary Key) to unambiguously distinguish them. → An identifier can be one or more attributes (e.g., first name, middle name, and last name) and would be called a Compound Primary Key. → Create an identifier if there is no obvious identifying attribute (e.g., part number) → Underline identifiers in diagrams
What is a data base?
A Database is a structured collection of records or data that is stored in a computer so that using query language can be accessed and answer queries Hierarchy of data elements Also Includes Metadata -Metadata describes the data base -Data about Data
Data Modeling
A database must mirror the real world if it is to answer questions about the real world. Data Modeling is a design technique for capturing the reality of data.
An Attribute
A discrete data element Describes an entity (i.e., is a characteristic) Meaningful (for the system being modeled) Attributes are the items of interest to the organization (the things being stored)
Relationships
A relationship is an association between the instances of one or more entities The degree of a relationship indicates the number of entities involved The cardinality of a relationship describes the number of instances of one entity associated with another entity
How do database application make databases more useful?
Allows organization to store, retrieve, and analyze information Is vital to an organization's success in running operations and making decisions
Hierarchy of Data Elements
Characteristics are grouped into attributes/fields Attributes are grouped into rows/records/etc. Rows are grouped into entities 1. Entity 2. Records 3. Attributes 4. Characteristics
What is a DBMS?
Database Management System -program creates, processes, and administers data base -usually licensed from vendors -Ex: Microsoft access, Oracle, Mysql, DB2 DBMS and Data base are two different things -Data bases is a structured collection of records or data that is stored in a computer system. The computer program that is used to manage and query a data base is known as a DBMS.
The Conceptual Model
Mainstream approach to conceptual modeling is the Entity Relationship Diagram (ERD) No standard notation Building blocks are entities, attributes, relationships, and identifiers (Keys) Emphasis - no data redundancy
Metadata
Metadata: -Data that describes data -Make Databases more useful -Make Databases easier to use Describe Data: -Field Name -Data Type -Find Description -Field Properties
What is the purpose of a database
Organize and keep track of things Keep track of multiple themes General rule: Single themes-Store in spread sheet Multiple Themes-Data Base
An Entity
Something of interest in the environment (e.g., person, place, thing, or concept) Represented in ERD by a rectangle An instance (row, record) is a particular occurrence of an entity
What is a NoSQL Database
Supports very high transaction rates Relatively simple data structures replicated on many severs in the cloud EX. Dynamo (Amazon), Bistable(Google), Cassandra (Facebook)
Relationships among records
Values in one table may relate to rows/records in other tables Keys: -Primary Key -Compound Key: No unique identifier in data -Foreign Key: Not a Primary key in all table, but in some -Secondary Key Data Base vs. Relational database