2. The Database Environment Flashcards
What are the components of a database environment?
- Users
- Database management systems
- Physical database
What are the advantages of a database?
- Reduces data redundancy
- Reduce costs of capturing data. Only entered once
- Data integrity is maintained and improved. Updates made in one place
- Improved data security, centrally controlled
- Application software independence. Data is stored separately from application software so updates won’t require rewriting.
- Standardization of data structures.
- Improved data access. Data made available to different users at the same time.
What are some disadvantages of databases
- Start up costs are large
- Database systems are complex to use
- Time-consuming to design
- A database failure will shut down the organization
Who are the different users of a database?
- End-users
- Application programmers
- Database administrator
- Data administrator
Who are the end users?
They capture data and extract information
Low skill level and use application software
What are the applications programmers for?
They are responsible for creating, maintaining, updating and managing application and DBMS software
What are the database administrators for?
- Responsible for controlling and managing database.
- Their roles include;
- implement and maintain standards
- Ensure application software complies with database management standards
- Define database structures
- Design and create databases in line with standards
- Implement, maintain and Evaluate access policies
- Monitor data and database access and security
- Monitor and maintain database performances
What is another name for a data administrator?
Database analyst
What are the data administrators responsible for?
- Managing and controlling data
- Manage integrity and setting and enforcing data standards
Are the database admin and data admin usually the same person?
Yes
What is a DBMS?
An integrated set of software that provides user friendly interface to users.
What is an example of DBMS?
Microsoft access
What are the functions of the DBMS?
- Design create and maintain database structures
- Control and organize data retrieval and and storage
- Capture, maintain and manipulate data
- Share data between multiple users
- Executes queries and generate outputs
- Control movement of data between users
- Control,and manage access
- Analyze and monitor database performance
Who suggests the three-level database architecture?
ANSI-SPARC
American national standards institute - standards planning and requirements committee
What are the three-levels of database architecture?
- External level
- Conceptual level
- Internal level
Is the three-level view of database architecture used commonly?
Yes
What is the external level also called?
The user view
He many different user views could there be?
An infinite amount
E.g. A creditor clerk’s user view screen will look different from a cash book input screen.
What is the conceptual level?
A complete view of the entire database and all it’s data.
Who will generally use the conceptual level view?
The database administrator
He many conceptual views of the database are there?
Only one
What is another name for an internal view?
Physical view
What is the physical view?
It is a low level view of how the data is physically stored, such as storage device like a magnetic hard drive.
He many physical views are there?
Only one
How is the binary code related to the physical view?
Is it only now facet of the physical view.
What does the database administrator do for all levels?
They update and maintain all three levels of the database architecture.
What are the key components of the DBMS?
- Data dictionary
2. Data languages
What is a data field?
A single data value and the smallest unit of data that can be accessed
What is a data dictionary?
Contains records for all data fields and can give a detailed description of all data fields
What does a data field description include?
- Name and description of data
- Other names the data field might have
- Data type
- Field length
- Software
- Source of data field
- Outputs in which it’s used
- The authorized user groups for that data field
What is a database language?
The different language that different users use to interact with the database
What are the different data languages Inlcuded?
- Data definition language
- Data control language
- Data manipulation language
- Data query language
What is the most common language used?
SQL (structured query language)
It combines the languages mentioned
What is DDL used for?
- Define a database and includes commands to;
- Create, modify and delete databases and database objects
- Define and describe database structures
- Create data dictionary
What do database objects include?
- Database tables
- Views
- Rules
- Indexes
Use usually uses the DDL?
The database administrator
What is the DCL used for?
To control the security and access to the database
Who uses the DCL?
Usually only the database administrator
What is DML use for?
Routine operations on the database, including insert, delete, modify and maintain the date stored on database.
Who can use the DML?
All users use it, usually accessed through application software
What is the difference between DDL and DML?
DML is to manipulate the data stored in the database where DDL is used to manipulate the database objects and structures.
What is DQL used for?
Usually to retrieve data from the database
Who can use DQL?
All users can use it. Usually through application software
What are database models?
The theoretical data structures
What are the main types of data models?
- Hierarchical
- Network
- Relational
- Object-orientated
- Multidimensional
When was hierarchical models used?
In earlier databases
What relationship did the hierarchical database have?
One-to-many relationship
Is the hierarchical structure flexible?
No
Inflexible
What is an example of a hierarchical database model?
Microsoft windows explorer
What is a network model?
A many-to-many relationship. Data may be accessed through many paths.
Is the use of a network model common?
No
Mostly obsolete
What does a relational model look like?
Data is stored on rows and columns, like a table.
What is the disadvantage of relational model?
It is slower than hierarchical and network because it uses more processing power to query data
What are the benefits of the relational model?
- Data can be accessed, inserted, deleted without changing the structure of the model
- Database can be adult customized
- Data does not need to be duplicated
- Most users can easily understand the structure
- It’s easy to search for and extract data
What is the most common structure?
Relational model, because of its many advantages.
Common in business and financial databases.
What is an object-orientated model?
Where data and the operations to be performed are stored in the database.
What is the benefit of object-orientated model?
Can further process more types of data beside text and numerical types. Such as video, audio and images.
Who would use object-orientated models?
More specialized databases such as web-based applications, molecular biology databases and defense industries
What is a disadvantage of object-orientated model?
It is used less because it is expensive and many organizations don’t need to process more data types besides text and numericals.
What is a multidimensional model?
Similar to a relational model, but with Merle dimensions, kind of creating a cube.
His data views from a multidimensional model?
Usually in a spreadsheet form.
What is an advantage of a multidimensional model?
It is easy to maintain.
What is the multidimensional model usually used for?
Usually storage warehouse
What does multidimensional models make possible?
- Online analytical processing (OLAP)
2. Business intelligence software (BIS)
How do we classify according to the physical location of the database?
Between;
- Centralized
- Distributed
What is a centralize database?
Where the database is stored in one location
E.g. One server
Hw do users interact with a centralized database?
Through networks
What is an advantage of centralized databases?
The information and data on them is up to date all the time provided online input and real-time processing is used
What is a distributed database?
Where there are several databases stored in different locations
What two different distributed databases a there?
Either;
- Partitioned
- Replicated databases
What is a partitioned database?
Where database is split into smaller parts and where a part is applicable to a user it will be made available to them.
When is partitioned database generally used?
Where data sharing isn’t necessary
E.g. Branches where customers don’t visit other branches
What is a replicated database system?
Where the original database is replicated at each location
What is an example of replicated databases?
Pharmacies where customers can use different branches to renew prescriptions etc.
How are the different databases updated in a replicated database system?
Either;
- Duplication
- Synchronization
What happens with duplication updating?
The master database is duplicated at regular frequencies.
What happens with synchronization of databases?
Much more complex, involves two way updating of master and distributed databases.
What is a data value?
A single character such as letters or numbers to populate a data field
What is a data field
Contain a single data value. Similar to a cell in a spreadsheet
What different data field can exist?
Compulsory,optional or calculated
What is an attribute?
Also seen as a column
Represent one unique characteristic of a collection of data fields
A field name?
Then name given to the attribute.
No attribute can have the same field name
Can different attributes have the same name?
No
What is a data record?
A set of related data field about a single member of an item
What is another name of a data record?
Tuple
Similar to rows in spreadsheets
What is a primary data field?
A unique data field that will identify the data records in a database
What else is a primary data field called?
Primary key
What is a foreign key?
Where a primary data field is entered into another database to create relationship between the two.
What is the purpose of foreign keys?
They prevent data from being duplicated.
What is another name for a database file?
A database table
What is a database file?
An organized collection of related data records
What are the different types of database files?
- Master
- Transaction
- Reference
- History files
What nature of records do master files contain?
Records of a relatively permanent nature. They do not change often.
What information do they master files contain?
Info about the organizations resources and subjects. E.g. Customers, suppliers, employees and inventory.
What do transaction files contain?
Data records of daily activities
He often are transaction files changed?
Regularly as new data is processed often
What is a replicated database system?
Where the original database is replicated at each location
What is an example of replicated databases?
Pharmacies where customers can use different branches to renew prescriptions etc.
How are the different databases updated in a replicated database system?
Either;
- Duplication
- Synchronization
What happens with duplication updating?
The master database is duplicated at regular frequencies.
What happens with synchronization of databases?
Much more complex, involves two way updating of master and distributed databases.
What is a data value?
A single character such as letters or numbers to populate a data field
What is a data field
Contain a single data value. Similar to a cell in a spreadsheet
What different data field can exist?
Compulsory,optional or calculated
What is an attribute?
Also seen as a column
Represent one unique characteristic of a collection of data fields
A field name?
Then name given to the attribute.
No attribute can have the same field name
Can different attributes have the same name?
No
What is a data record?
A set of related data field about a single member of an item
What is another name of a data record?
Tuple
Similar to rows in spreadsheets
What is a primary data field?
A unique data field that will identify the data records in a database
What else is a primary data field called?
Primary key
What is a foreign key?
Where a primary data field is entered into another database to create relationship between the two.
What is the purpose of foreign keys?
They prevent data from being duplicated.
What is another name for a database file?
A database table
What is a database file?
An organized collection of related data records
What are the different types of database files?
- Master
- Transaction
- Reference
- History files
What nature of records do master files contain?
Records of a relatively permanent nature. They do not change often.
What information do they master files contain?
Info about the organizations resources and subjects. E.g. Customers, suppliers, employees and inventory.
What do transaction files contain?
Data records of daily activities
He often are transaction files changed?
Regularly as new data is processed often
What is a replicated database system?
Where the original database is replicated at each location
What is an example of replicated databases?
Pharmacies where customers can use different branches to renew prescriptions etc.
How are the different databases updated in a replicated database system?
Either;
- Duplication
- Synchronization
What happens with duplication updating?
The master database is duplicated at regular frequencies.
What happens with synchronization of databases?
Much more complex, involves two way updating of master and distributed databases.
What is a data value?
A single character such as letters or numbers to populate a data field
What is a data field
Contain a single data value. Similar to a cell in a spreadsheet
What different data field can exist?
Compulsory,optional or calculated
What is an attribute?
Also seen as a column
Represent one unique characteristic of a collection of data fields
A field name?
Then name given to the attribute.
No attribute can have the same field name
Can different attributes have the same name?
No
What is a data record?
A set of related data field about a single member of an item
What is another name of a data record?
Tuple
Similar to rows in spreadsheets
What is a primary data field?
A unique data field that will identify the data records in a database
What else is a primary data field called?
Primary key
What is a foreign key?
Where a primary data field is entered into another database to create relationship between the two.
What is the purpose of foreign keys?
They prevent data from being duplicated.
What is another name for a database file?
A database table
What is a database file?
An organized collection of related data records
What are the different types of database files?
- Master
- Transaction
- Reference
- History files
What nature of records do master files contain?
Records of a relatively permanent nature. They do not change often.
What information do they master files contain?
Info about the organizations resources and subjects. E.g. Customers, suppliers, employees and inventory.
What do transaction files contain?
Data records of daily activities
He often are transaction files changed?
Regularly as new data is processed often
