Chapter 17 Relational Databases and Normalisation Flashcards

1
Q

How can data be entered into a database?

A
  • web based forms
  • paper forms
  • automated devices
  • OCR
  • OMR
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2
Q

What is the main advantage of having web based forms?

A

Can have very strong validation for data being entered

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3
Q

What is the main disadvantage of paper forms?

A

Prone to mistakes, so people are asked to enter data twice

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4
Q

What are some examples of automated devices?

A

barcode scanners, smart card readers

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5
Q

What does OCR stand for and what is it?

A

optical character recognition used for handwritten character recognition

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6
Q

What does OMR stand for and what is it?

A

Optical mark recognition, captures human entered data from forms

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7
Q

What are the names of files that can be used to store captured data? - data that can be in a database

A
  • serial files
  • sequential files
  • indexed sequential files
  • random/direct access files
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8
Q

What is a serial file?

A

Stores data in entered order, there is no order enforced

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9
Q

What is a sequential file?

A

stores data in order of the key field, order is enforced

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10
Q

What is a indexed sequential file?

A

Stores data in order of the key field with an index to allow groups of records to be accessed quickly

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11
Q

What is a random/direct access file?

A

Data entered is given a unique record number that can be used to access that data

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12
Q

What does DBMS stand for?

A

database management system

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13
Q

What are some examples of DBMS?

A

Microsoft Access

Oracle

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14
Q

What is a DBMS?

A

A software application with many features used for dealing with databases

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15
Q

What are the features of a DBMS?

A
  • creates interface for user
  • allows queries
  • reports
  • additional security
  • enforces integrity of data (referential integrity)
  • interact with other software applications
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16
Q

What additional features can a DBMS administrator do?

A
  • provide centralised backup
  • assign user access levels
  • create logon and passwords for database
  • updates to DBMS
17
Q

Normal form of displaying a table/relation/entity?

A

entity(attribute one, attribute2 , attribute3)

18
Q

What does it mean when in the form above something is underlined?

A

It means it is the primary key

19
Q

What does it mean when something in this form is overlined?

A

It means there is more than 1 piece of data in this attribute.

20
Q

What does it mean when there is an asterisk next to an attribute in this form?

A

Means that attribute is a foreign key.

21
Q

What is data integrity in a database?

A

The correctness and consistency of data along the whole database

22
Q

What is referential integrity?

A

A concept of a database where consistency between linked tables is kept. It enforces an action on linked table based on the action on the primary and vice versa.

23
Q

Techniques used by the concept of referential integrity?

A
  • update , when a record is updated, all records pointed to by the foreign key will also be updated to the same values
  • delete , when a record in primary table is deleted, all records pointed to by foreign keys in other tables will also be deleted
24
Q

What is normalisation?

A

formal process involved in the design of an efficient relational database?

25
Q

Can a flat file database be normalised?

A

No if we want it to be a flat file database. It would turn into a relational

26
Q

Normalisation means that entites are organised in such a way that:

A
  • there is no data redundancy
  • there is no data inconsistencies (due to being a relational and no data redundancy)
  • complex queries can be made
  • structure of entites allow unlimited records to be added
27
Q

What form of normalisation do we have to know?

A

1NF 2NF and 3NF

28
Q

What does 1NF require?

A

Contains no more than one piece of data in a field under an attribute

29
Q

What do we have to do to 1NF?

A
  • create new relations to seperate all attributes which have fields which have more than 1 piece of data
  • all single value attributes are kept wihin original relation/table/entity
30
Q

What is 2NF and what does is require?

A

2nd Normal Form - requires 1NF and requires that all key attributes are dependent on the composite key, not only partially

31
Q

What do we call 2nf?

A

Partial dependency test

32
Q

What do we do to undergo 2NF?

A
  • seperate any attributes which are not fully dependent on composite key
33
Q

What is 3NF and what does it require?

A

3rd normal form, requires 2NF and seperate any attributes which are dependent on other non-key attributes, foreign keys are retained tho

34
Q

Overall what does 3nf mean?

A

All attributes are dependent on the key, the whole key and nothing but they key.

35
Q

To complete 3NF we have to ?

A
  • separate any attributes which are dependent on any other non-key attributes while foreign keys are retained
  • check each attribute make sure it is derived from the primary key otherwise create new relation
36
Q

Advantages of Normalisation?

A
  • no data redundancy
  • no inconsistencies
  • easier to maintain and induce changes
  • maintenance of integrity is easier (usually enforced)
  • smaller tables mean faster searching,sorting,indexing and querying
  • saved storage space (due to no redundancy)