Relational Databases

File
1. Table
  1. Record
    1. All data about one person or thing.
      1. Quite a few fields can be used to make a record e.g. name, address,age,date of birth.
  2. Field
    1. Primary Key
      1. A field in a table which is unique and this helps to identify records or people
      2. Referential integrity
        Every foreign key value has a matching value in the appropriate primary key field.
    2. A piece of data related to a person or thing
    3. Foreign keys
      1. A primary key in one table inserted as a normal field in another table
    4. Attributes- Name,Age,Address
  3. Records are stored in here.
  4. Made of quite a few pieces of information, e.g. First Name, Address, Age
  5. Entities- objects,people,things
  6. RelationShips:
    1. One to Many
      1. Where one entity can have many relations- such as 1 doctor has many patient or 1 student has many exams
    2. Many to many
      1. where many entities can have many relationships e.g. 1 video can be hired by several customer BUT those customers can hire several videos
    3. One to One
      1. When one entity can only be related to one entite e.g. 1 man has 1 wife.
2. Many tables are stored in a file, this is the database.
Vast amounts of info can be stored!
Queries can be run to search for specific records.
1. Searching is what a query does.
  1. Parameters are just search criteria
  2. 4 Types
    1. Static-the parameters stay the same for ever.
    2. Dynamic- you can change the search result sto what you need
    3. Simple- only 1 parameter is used at a time
    4. Complex-more than one parameter is used
Reports can be created from data stored or queries run
1. presents data taken from a query or from tables in a preformatted attractive manner
Validation can be used to reduce errors.
1. Validation!
  1. Makes sure that the data is: accurate sensible,within acceptable boundaries.
    1. Range Check- makes sure that the value entered is between 2 preset boundaries
    2. Lookup Check-Allows only a limited amount of item to be selected
    3. Length Check- checks that the data entered is a certain length.
    4. Presence check- makes sure something is enteredin the field
  2. NEVER MAKES SURE THAT THE DATA IS CORRECT!!!
2. Verification
  1. Making sure that the data on the source document is the same as the object doucument.
    1. Proof Reading- double checking your work basically.
    2. Double entry- where two people input the same document and these are then compared any differences are then noted and rectified.
Forms Used to enter data.
1. A window/Screen with multiple spaces to enter data.

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	Criado por BadSideSecret mais de 10 anos atrás