Chapter 5---Database Processing

The purpose of database is to keep track of things. A database is a self-describing collection of integrated records. A byte is a character of data. In a database bytes are grouped into columns . Columns are also called fields. Columns are grouped into rows, which are also called records. A group of similar rows or records is called a table or file.
Foreign keys- a column or group of columns used to represent relationships.
Databases that carry their data in the form of tables and that represent relationships using foreign keys are called relational databases. Metadata are data that describe data.
Components of a Database Application System: User---->Database Application: Forms,Reports,Queries,Application Programs----> Database Management System(DBS)----> Database: Tables,Relationships,Metadata.
A database management system is a program used to create,process, and administer a database.
Structured Query Language(SQL) is an international standard language for processing a database.
Database Administration is the management,development,operation, and maintenance of the database so as to achieve the organizations objectives.
A database application is a collection of forms,reports,queries,and application programs that process a database.
Data entry forms are used to read,insert,modify, and delete data.
Multi-user processing is when multiple users process the database at the same time.
Lost update problem is an issue in multi-user database processing in which two or more users try to make changes to the data but the database cannot make all those changes because it was not designed to process changes from multiple users.
Enterprise DBMS products process large organizational and workgroup databases.
Personal DBMS products are designed for smaller,simpler database applications.
Data model is a logical representation of the data in a database that describes the data and relationships that will be stored in the database.
The entity-relationship (E-R) data model is a tool for constructing data models. An entity is some thing that the users want to track. Ex: Order,Customer,Salesperson.
Entities have attributes that describe characteristics of the entity. Ex:Order, Subtotal,Tax
Entities have an identifier which is an attribute whose value is associated with one and only one entity instance. Ex: order number is an identifier of order. Entities have relationships to each other. Ex: An order has a relationship to a customer entity and also to a salesperson entity.
One-to-many relationships- one department can have many advisers,but an adviser has at most one department.
Many-to many relationships- one adviser can have many students and one student can have many advisers.
Normalization is the process of converting a poorly structured table into two or more well-structured tables.
Data integrity problem - in a database, the situation that exists when data items disagree with one another. Ex: two different names for the same customer.
Data aggregators - companies that obtain data from the public and private sources and store,integrate, and process it in sophisticated ways.