GCSE Computer Science: Database

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Zusammenfassung der Ressource

GCSE Computer Science: Database
  1. Entity
    1. An entity is a person or physical thing about which data is held in a database
    2. Field
      1. An individual box in the data table
        1. Table = The whole thing
      2. Record
        1. An entire row of data
        2. Database management system / DBMS
          1. Allows you to create a table
            1. Componants
              1. Tables
                1. Forms
                  1. Queries
                    1. Reports
                      1. Modules
                        1. Program within an application that performs a specific task which cannot be done by simply making a query or report
                    2. Datatypes
                      1. Text
                        1. Integers
                          1. Numbers with a decimal
                            1. Dates
                              1. Currency
                                1. Yes/No fields
                                2. Primary Key
                                  1. One field is designated as the p.k
                                    1. Each record must have a different value in the p.k
                                      1. Uniquely identifies the record
                                      2. Validating Fields
                                        1. Minimise errors when data is entered into the database
                                          1. Specifying a rule that the data must obey
                                            1. Range check
                                              1. Type check
                                                1. e.g. number
                                                2. Presence check
                                                  1. Data entered in the field
                                                  2. Format check
                                                    1. List check
                                                      1. Must be item on predefined list
                                                  3. Data Redundancy
                                                    1. Holding more data than necessary
                                                      1. Takes time and space
                                                        1. Can result in inconsistent data
                                                        2. Each entity has an attribute
                                                          1. Attribute = Field in the table which describes the entity
                                                            1. One-to-one
                                                              1. e.g. husband/wife
                                                              2. One-to-many
                                                                1. e.g. mother/children
                                                                2. Many-to-many
                                                                  1. e.g. pupils/subjects
                                                            2. Separation of Data
                                                              1. Data held about various entities are held separatly from the applications that use it.
                                                                1. e.g. many departments in a school can look at or use the data
                                                                2. Reduces data redundancy
                                                                  1. Data is consistent
                                                                    1. Saves storage
                                                                    2. Database
                                                                      1. Persistent, organised store of data
                                                                        1. Persistent = Data stored on a non-volatile storage device
                                                                          1. Organised = Structured into tables
                                                                          2. Allows separation of data between applications and the database
                                                                            1. Allows multiple applications to use a single database
                                                                              1. Can allow many users to simultaneously access the data and it's applications
                                                                                1. Provides security in terms of access rights
                                                                                  1. Can provide automatic backups
                                                                                  2. Reports
                                                                                    1. Useful feature of a DBMS
                                                                                      1. Reports are produed based on queries
                                                                                        1. When a user asks for a report based on a query, the query will automatically be run first using the latest data, so the report is up-to-date
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