Study Notes
Sample Problems:
A sales manager might want to see a listing of the sales made by Salesperson 100. Each record in the file had to be examined by the computer to determine if it was a Salesperson 100 record. If so, it was selected and used to print the report. A file containing thousands of records might include only a dozen or so for Salesperson 100, but every record in the file had to be scanned.
Question: Was this an efficient approach? Why? Why not?
When a firm adopts a database concept, what will the hierarchy look like?
Question: A record that has subsidiary records is called the ______ and the subsidiary records are called _______. (hint: think of family)
Problem: Assume that the following records compose the entire Customer Master file and that a user need information by salesperson. Enter the link fields. What is the primary key field? What establishes a record? A field? A file?
Customer # Year to date sales salesperson # Salesperson link
104 25,000 33
109 17,500 17
111 12,500 33
118 6,000 33
124 12,000 49
127 300 14
132 18,000 49
138 24,000 33
142 26,500 14
149 120 17
151 8,000 14
Questions: How would you establish an explicit relationship with the above problem? What would the link field be? Remember, once you retrieve a salesperson record, the link in that record can lead you to another record that is logically related to that salesperson. A link field in the second record lead to a third record and so on, creating a chain reaction through an entire set of files. What would create this chain reaction? What would that link be?
(Hint: The answer lies in this puzzle "A rose by any other name is still called a rose")
Things to Remember:
In a traditional file environment, all files are flat sequential files.
The presence of duplicate data in multiple files is referred to as data redundancy.
A data element added to a record to tie it to another record is a pointer.
Structured query language is data manipulation language.
A collection of data organized to serve many applications is a database.
In a DBMS the component that is used by programmers to specify the content and structure of the database is the data definition language.
In a DBMS the physical view is the perspective of the information systems specialist.
In the hierarchical the DBMS the root segment is the uppermost segment.
Parent-child segments in a hierarchical DBMS are linked together by pointers.
One advantage of hierarchical and network DBMS is efficient transaction processing.
Hierarchical and network DBMS are considered inflexible because all access paths, directories, and indices must be specified in advance.
The Relational DBMS is the most suitable model for processing ad-hoc requests for information.
A Relational DBMS can relate any data element in one table to any data element in another as long as the two tables share a common data element. (This will help you with the problem)
A Distributed database can have data stored at more than one location and quickens response time.
The most prominent data manipulation language today is SQL.
An object oriented database stores data and procedures together.
Describe the components of a database management system.
Describe the three major database models that are used to organize data in a database?
Which DBMS is better at processing structured, routine requests rather than at handling ad-hoc queries?