2. The Database Environment Flashcards
What are the components of the database environment?
- Users
- Database management system (DBMS)
- Physical database (including hardware and data)
What does the database management system diagram look like?
From multiple users -> multiple application softwares -> single database management software -> single physical database
What is the mnemonic for advantages of a database?
Red cost Intel secure independence, Stanley accessed.
What are the advantages of a database ?
- Reduced data redundancy
- Lower capturing costs, data entered once
- Integrity of data maintained, updates occur same place
- Increased security, centrally controlled
- Data is independent from application software
- Standardization of data structures
- Access to data is easy
What is the mnemonic for disadvantages of a database?
Costa complexly times failures
What are the disadvantages of databases?
- Costs to start up
- Complex to design and use
- Time-consuming to design
- Failure of the database would mean failure of application software and may result in shut down of organization
Who are the various database users?
- End user
- Application programmer
- Database administrator
- Data administrator
How do end users use the database?
They capture data and extract informatiom
Low skill level, they use application software
What are application programmers responsible for?
Creating, maintaining, updating and managing application and DBMS software
What is the responsibility of the database administrator?
Managing and controlling the database
What is another name for a data administrator?
Database analyst
What are data administrators responsible for?
Controlling and managing data
Manage integrity of data by setting standards
What is DBMS?
Integrated set of software that provides a user friendly interface to users
What is an example of DBMS?
Microsoft access
What are the levels of the three-level database architecture?
- External level
- Conceptual level
- Internal level
What is another name for the external level of architecture?
User view
What is the external level?
End users view of data and database
How many view can the external view have?
An infinite amount
E.g. Cash clerk will have a different input screen than a credit sales clerk etc.
What is the conceptual level?
A complete view of the entire database and all the data
Who normally uses the conceptual view?
The database administrator
How many variations are there of the conceptual view?
Only one
What is another name for the internal level?
Physical view
What is the internal view?
It is the low level view of how the data is stored physically. E.g. Harddrive etc.
How many physical views are there?
Only one
How is binary code concerned with the physical view?
Binary code is only one facet of the physical view
Who updates and manages all levels of database architecture?
The database administrator
What are the key components of the DBMS?
- Data dictionary
2. Data language
What is a data field?
A single data value, it is the smallest unit of data
What is a data dictionary?
Contains records for each data field and provides detailed description of each data field
What are database languages used for?
The users to interact with the database
What are the database languages included?
- Data definition language
- Data control language
- Data manipulation language
- Data query language
What is SQL?
Structured query language and combines all previously mentioned languages
What is the data definition language used for?
Define a database and includes commands to:
- Create, modify and delete database and it’s objects
- Define and describe data structure
- Create data dictionary
What are data objects?
- Tables
- Views
- Rules
- Indexes
Who usually uses DDL?
The administrator
What is the purpose of the data control language?
Used to control security and access to database objects and data
Who uses the DCL?
Only the database administrator
What is DML used for?
Used to insert, maintain, delete and modify data store in database
Who uses the DML?
All users of the database. Usually used through application software
What is the difference between the DDL and DML?
The DML is for the data stored where DDL is for the objects on the databas
What is DQL used for and who uses it?
Used to extract information and used by all users
What is the definition of a database?
Organized collection of related data that is stored and managed electronically and can provide data to different application software
What is a database model?
Theoretical data structure
What are the different database models?
- Hierarchical
- Network
- Object-orientated
- Relational
- Multidimensional
What relationship does a hierarchical database model have?
One-to-many relationship
What is wrong with the hierarchical model?
It is very inflexible
What is an example of a hierarchical model?
Microsoft windows explorer
What kind of relationship does a network model have?
A many-to-many relationship. Data can be accessed through different paths
Is the network model used often?
No it’s mostly obsolete now
What is a relational model?
Data is stored on two dimensional rows and columns like a table
What is a disadvantage of relational model?
It processes data slower and slower to retrieve data
What are the benefits of relational model?
- Data can be modified without changing the data structure
- Structure can be easily customized
- Data doesn’t need to be duplicate
- Most users can easily understand it
- It is easy to find data
What is object-orientated model?
Where data and it’s operations are stored in the database
What is a benefit of object-orientated model?
Is can process more type of data like images, audio, video etc.
Where would object-orientated models be used?
For more specialized databases such as multimedia web based applications and molecular biology databases and defense industries.
What is a disadvantage of object-orientated model?
Expensive to implement and most businesses wouldn’t need to process all types of data besides text
What is a multidimensional databases?
It’s like a relational model but with more dimensions.
What does the multidimensional model look like?
It has a cube-like structure
What is an advantage of multidimensional database?
Easy to maintain
What is multidimensional model used for?
Mainly for data warehouses
What does multidimensional models give rise to?
- Business intelligence software
2. Online analytical processing
What are the classifications of physical location of storage?
- Centralized
2. Distributed
What is centralized database?
All data is stored in one location e.g. A server
How do users interact with a centralized database?
Through networks
What is an advantage of centralized database?
All data is immediately up to date
What kind of input and processing is used for centralized database?
- Online input
2. Real-time processing
What are distributed databases?
Several interlinked databases tried on different computer in different locations
What are the two different distributed databases?
- Partitioned
2. Replicated
What is a partitioned database?
A database split into smaller parts and the parts applicable to certain users will be made available to them at the nearest location
When would a partitioned database generally be used?
When there is a minimal necessity for users to share data
Example of places using partitioned database?
Branches don’t need to share customers info with each other
What is a replicated database?
Where the original database is replicated to all locations
Example of business using replicated database?
Pharmacy nationwide, where customers have scripts
What are the methods to update different replicated databases?
- Duplication
2. Synchronization
What is duplication?
Where master database is duplicate to all other databases at a specific frequency
Rewrites all databases
What is synchronization?
This involves a two way update between master database and distributed databases
What is the most common database model used?
Relational database
What is a data value?
Characters that populate a data field
What is a data field?
Contains data value
Similar to a cell
What is an attribute?
Similar to a column in spreadsheet
What is a field name?
The name of all attributes
What is a data record?
A row
What is a primary data field?
Primary key
Unique data field that identify data records
What is a foreign key?
A data field entered into another data record to create a relation between the two
What are the purpose of foreign keys?
To prevent duplication of data
What is a database file?
Also known as database table
Collection of data records
What are the types of database files?
- Master
- Transaction
- Reference
- Histroy
What is a master file?
Data records that contain info of a semi-permanent nature. They don’t change regularly.
What info is contained in master files?
Info about organizations sources and subjects.
E.g. Customers, suppliers, inventory, employees
What are transaction files?
Files containing records relating to daily activities. They change regularly
