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Flashcards

Chapter 5 - computing

Eloise Bridges Science GCSE Inglês 52 flashcards

Flashcards do conjunto (52)

  1. 1Data Models What is a data model?The way in which data is constructed
  2. 2what is a databasea database a persistant
  3. 3Database design When designing a database you have to make a decision about each field... list the four fieldsData type- the program needs to know how to handle the data. The choice made will affect what processing can be done
    Field size- There is no point reserving more bytes for each field than are necessary
    Validation - Rules can be set up to filter out some types of mistakes
    Key filed make at least one file to make a primary key
  4. 4What is a schema?Definition of a database
  5. 5What is a Data dictionary?The stored schema of a database
  6. 6Why is sharing data importantSo that more than one person can open and work with a data file at once.
  7. 7What is criteria for sharing dataprotect data from damage and unintended deletion
    Protect data form unauthorised access
    Make sure that all who need to access it can
    make sure data is accurate and up to date
  8. 8What is an DMBS and why do people use it?a database management system, Making sure the design of database are as robust and flexible as possible. This is software that handles the data directly and provide interface to the apllications
  9. 9what is an external view of a database?can present a subject of data to those who need it.It is what the user can see.
  10. 10What is a conceptual viewThis view of a database is for the designer. It shows how the component parts of the database are constructed and fit together well. It can be used to create the database in a visual way
  11. 11What is an internal viewThe dta is stored as a string of bites. The dmbs makes it possible for most of the designers and users to ignore this detail and work more easily with what interests them
  12. 12What is concurrency. What is used to prevent concurrency problems?the availability of something to many people
    A DMBS uses a record locking mechanism,when one user is looking at a record this record becomes locked to any others
  13. 13WA database is a persistent organised store of data on a computer system
  14. 14Why does a computer system need to organised?So that the computer system easily select and edit data items
  15. 15What does persistent mean?It is stored in secondary storage so it can be accessed later
  16. 16What does a database software have to be able to do ?create, recieve and update and delete the data in a database
  17. 17What can this be referred to as ?Crud
  18. 18What are most computer systems made to do?and whystore ,process and retrieve data , as this is what they were made to do and it is why most organisation buy them
  19. 19What is a serial file?A file of items one after another. All you need to do is start at the first data item, examine, it if it is what is looked for print it otherwise move on to the next one
  20. 20What is a sequential file?The data is in order( in a sequences) , well known algorithms such as binary search can quickly find items in a ordered file.
  21. 21How does it work?by looking at the middle record and deciding whether the wanted item is before or after it, and the repeating the process
  22. 22Why is this process quick?after each step amount of data liked at is halved, it doesn't take that long before data is found or for it to be clear that data is not there
  23. 23What is an indexed sequential file?A sequential file that is accessed using index which is a separate file
  24. 24What is a flat file database?Database consisting of only one table
  25. 25What is a field?A characteristic of something stored in a database.
  26. 26What is a record?All the data about one item in a database
  27. 27What would need to happen if a company decides to add more information?Software would need to be rewritten and the data files completely changed to process additional information
  28. 28what is a entity?something that we store data in a database
  29. 29What is an attribute?A characteristic of an attribute becomes a field in a data table
  30. 30What is data redundancy?The unnecessary repetition of data
  31. 31What can it lead to?complex programming problems because each instance of repeated data has to be updated
  32. 32what is data integrity?The state of data is as expected, reflecting reality
  33. 33what is validation?The process of checking data as it is input to ensure that it is reasonable can be done by using data handling software that will reject any data that does not conform to specified rules.Validation does not detect all errors only if rules are broken
  34. 34What is verification?The process of checking whether data is true or correct
  35. 35Give an example of a more reliable method rather than a human expectation?enter the same data twice, using two operators. The software can compare two versions and highlight any differences
  36. 36Give some examples of were data is entered by a machine to make the process more accurate and fast?Bar codes, Magnetic strips, Smart Cards
  37. 37What is a transaction?A change to a database
  38. 38Why must transactions be controlled?to prevent conflicting changes being made
  39. 39How is this ensured?every transaction must be confirmed to what are called the ACID rules
  40. 40What is ACID?A set of rules that protects a database from errors during transactions
  41. 41What is Atomicity?Means that the transaction is either completely carried out or not at all. A transaction may involve several step. If part of a transaction fails the whole transaction fails and the database remains in its original state
  42. 42What is consistency?A transaction must take the database from one valid state to another, it must not break any rules.
  43. 43What is isolation?No transactions may interfere with any other transaction. So it would normally not be possible for two transaction to be carried out at the same time on one record because the results would be unpredictable
  44. 44What is Durability?Once a transaction has been committed, it must remain so, even in case of an error or power fail
  45. 45Features offered by DMBS? What are queries?objects that extract data from a base. Thye are used to select fields required and the conditions that need to be met
  46. 46Give an Example of a common way to create a query?use an interactive graphic tool called a Query by example. This allows to drag in the tables you want to query and enter the criteria you need to select
  47. 47Why is QBE not always the best way to create a query?Programmers may have more controlover what they do by writing a query using a query language. SQL(Structured query language) is a popular one and some Dmbs have there own sql capability
  48. 48What are some of the key words used in sqlAND- used to link a statements
    OR- if someone want to select datt based on two conditions being true
  49. 49Why are SQL queries not directly used to find or change data?requires programming expertise and would take a lot of time.
  50. 50What is used instead?On screen forms are usually provided for users so that the information needed is easy to see and modify. Forms can be made user friendly and sit at the top of hidden programming code
  51. 51What is a report?These are often printed outputs of data from a database. They can be tables of data or fully formatted and well presented reports for management. Usually based on queries that have done the work of extracting and collecting the fields required
  52. 52What Is data mining?When a company has a very large collection of data, It can represent a valuable resource in ways the company would never anticipated. Data mining is using software to trawl through data form many sources, looking for connections.

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GCSE Science FlashCards sobre Chapter 5 - computing, criado por Eloise Bridges em 22-12-2016.
Criado por
Eloise Bridges
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