PROCESSING INFORMATION IN THE FORM OF TRANSACTIONS
Such as payroll processing, order processing, and handling your registration requests for classes.
This is called ONLINE TRANSACTION PROCESSING (OLTP) - the gathering of input information, processing that information, and updating existing information to reflect the gathered and processed information.
Information Revisited 4-7 Most importantly, managing information includes organizing it so that people can logically use it without having to know anything about its physical structure. The difference between logical and physical is key.
You organize and access a database by its logical structure, not its physical position.
DATA DICTIONARY - contains the logical structure of information in a database.
The data dictionary contains the logical properties that describe information in a database.
See Figure 4.5 (page 126) for the data dictionary of the Percentage Markup field in the Inventory database.
A Database Has Logical Ties Among the Information
A PRIMARY KEY is a field in a database file that uniquely describes each record.
A FOREIGN KEY is a primary key of one file that also appears in another file. So, foreign keys specify how files are logically related.
For example, the Part and Facility files are logically related. So, in Figure 4.4 you can see that Facility Number (the primary key for the Facility file) exists in the Part file (where it’s a foreign key).
A Database Contains Built-in Integrity Constraints
An INTEGRITY CONSTRAINT is a rule that helps assure the quality of the information in a database.
A registration database at your school includes integrity constraints concerning prerequisites for certain classes.
Our Inventory database includes an integrity constraint that says a part in the Part file cannot be assigned to a facility that does not exist in the Facility file.
PHYSICAL VIEW deals with how information is physically arranged, stored, and accessed on some type of secondary storage device.
LOGICAL VIEW focuses on how you need to arrange and access information to meet your particular business needs.
DBMSs accepts logical requests from the various other DBMS subsystems, converts them to their physical equivalent, and actually accesses the database and data dictionary as they exist on a storage device. 4-15
QUERY-BY-EXAMPLE (QBE) TOOL - helps you graphically design the answer to a question. Figure 4.10 (page 130) shows the QBE for displaying the names and phone numbers of facility managers in charge of parts that cost more than $10.
STRUCTURED QUERY LANGUAGE (SQL) - a standardized fourth-generation language found in most database environments. SQL is the same as QBE, except that you perform a query by creating a statement instead of pointing, clicking, dragging.
This model takes advantage of the concept of an OBJECT - a software module containing information that describes an entity class along with a list of procedures that can act on the information describing the entity class.
Figure 4.15 (page 138) shows the same video rental store using the O-O database model.
Notice that the objects (entity classes) - which include Customer , Video Rental , Video , and Distributor - contain both information and procedures for working with that information.