Chapter 8 : Databases

Question 1

What are the benefits of using DLLs

Answer 1

Executable file is smaller…only loaded to memory when needed

Changes done independently on main program…no need to recompile

One file is available to several applications…saves space

Question 2

What is a Dynamic Link Library File

Answer 2

Shared library file

Code only loaded to main memory when required of run time

Made available to several applications at the same time

Question 3

What are the disadvantages of DLL

Answer 3

Malicious changes can install to users computer

Unexpected changes means program stops working as expected

File must be present or else unable to find errors

Question 4

What are the benefits of using library routines

Answer 4

Code already written…programer saves time

Code used by many people…thoroughly tested

Programmer can use functions they may not know…simplifies program

Conform to industry standards…more robust

Question 5

What is an entity

Answer 5

An object about which data can be stored

Question 6

What is a primary key

Answer 6

The unique attribute / combination of attributes used to identify the
record / tuple

Question 7

What methods can be used to secure a database

Answer 7

Backup / recovery procedures

Use of access rights

Views

Record and table locking(prevents simultaneous access to data to prevent over writing)

Encryption

Question 8

How do you put a database into 1NF

Answer 8

Identify repeating groups of attributes …

Ensure each field is atomic

Identify the primary key for the table

Question 9

What is a data dictionary

Answer 9

Stores data about the database like metadata

Field names,Table names,Datatypes

Question 10

What things are included in defining a table

Answer 10

 CREATE TABLE start and end bracket

  CREATE TABLE BIRD_TYPE( 

  );

Define Records and datatypes
Name VARCHAR(9),

 Set primary key

 PRIMARY KEY (BirdID)

Question 11

Describe how using a relational database has overcome the previous problems
associated with a file-based approach.

Answer 11

• By storing data in (separate) linked tables data redundancy is reduced / data duplication is controlled…
• Compatibility / data integrity issues are reduced as data only needs to be updated once / is only stored once.
• Unwanted or accidental deletion of linked data is prevented as the DBMS will flag an error.
• Program - data dependence is overcome.
• Changes made to the structure of the data have little effect on existing programs.
• Ad-hoc / complex queries can be more easily made as the DBMS will have a query
  language/ QBE form.