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Summary A* 9618 Chapter 8: Databases £3.49   Add to cart

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Summary A* 9618 Chapter 8: Databases

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8.1 Database concepts 8.2 Database management system (DBMS) 8.3 DDL and DML Helped me get A*

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  • Chapter 8 : databases
  • September 10, 2024
  • 14
  • 2022/2023
  • Summary
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8 Databases

8.1 Database concepts

Show understanding of the limitations of using a file-based approach
for the storage and retrieval of data

Data stored in discrete files, stored on computer, and can be accessed,
altered or removed by the user.

Limitations of File Based System:

No enforcing control on organisation/structure of files

Data Redundancy:

Data repeated/duplicated in different files

manually change each

Inconsistent data

Memory wastage

Fixed queries

Programs are written to satisfy particular functions

Sorting must be done manually or must write a new program

Incompatible file formats

Data may be in different format; difficult to find and use other
files.

Impossible for it to be multi-user; chaotic

Security not sophisticated

users can access everything

Each user should only be allowed to access data concerning
their requirements only.




8 Databases 1

, Describe the features of a relational database that address the
limitations of a file-based approach

In a file-based approach, the record structure is fixed, however, in a
relational database, attributes can easily be added/deleted.
Relational databases have a query generator which can reduce the time
taken to produce a new query, in a file-based approach a new program
must be created to produce a query.



Reduced data redundancy/duplication

Data is stored in separate linked tables

Reduced data dependency

Program-data independence

Changes to the data(design) do not require changes to
programs.

E.g. fields can be added or removed without effecting existing
programs

Improved data integrity

Data only needs to be updated once/is only stored once which
also improves data consistency.

The DBMS uses its data dictionary to perform validation checks
on data entered.

Improved security

Each user can be given access rights so it can only access the
data it needs.

Data privacy is maintained.

Complex queries are easily done

Complex queries can be more easily made as the DBMS will
have a query language

Ability to create ad hoc queries

Allow concurrent access




8 Databases 2

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