Intro Databases

Question 1

Database:

Answer 1

organized collection of data

Question 2

Database models:

Answer 2

describes how data is organized within a database

Question 3

Flat file model: data organized into table-like structure. Elements are in rows called records and columns called fields.

Answer 3

Problem w/ flat file:
Data redundancy problems: repeated data

Data integrity problems: accidental spelling mistake, incorrect information

Update/Delete problems: making changes is time-consuming because the user has to go through every row

Insert problems: new information cannot be added (e.g. new employee cannot be added to database until after 1st shift)

Question 4

Hierarchical database model:

Answer 4

organized into tree-like structure. Node is related to many child nodes in its lower level, but is always connected to a single parent node at the higher level

Causes less data redundancy and easier to maintain data integrity
Search operations can be slow
Database still used in XML files

Question 5

Network database model:

Answer 5

extension of hierarchical model except a node can have many connections at both levels (high and low)

Difficult to implement in computers

Question 6

Relational database model:

Answer 6

introduced by E.F. Codd (1970), most commonly used model. Data is organized into a set of tables (entities) that are related to one another by using special columns called keys

Solves data redundancy problems: data is not repeated

Solves data integrity: allow only authorized people to make changes, incorrect data items cannot be entered

Solved update/delete problems: can update specific data without making changes in other connected tables

Solves insert problems: new worker is allowed to be added even if they have not had a shift