Relational Databases

Relational Databases

1. TABLES

   • Record
     • All data about one person or thing.
       • Quite a few fields can be used to make a record e.g. name, address,age,date of birth.
   • Field
     • Primary Key
       • A field in a table which is unique and this helps to identify records or people
       • Referential integrity
         • Every foreign key value has a matching value in the appropriate primary key field.
     • A piece of data related to a person or thing
     • Foreign keys
       • A primary key in one table inserted as a normal field in another table
   • Records are stored in here.
   • Relationships:
     • One to Many
       • Where one entity can have many relations- such as 1 doctor has many patient or 1 student has many exams
     • Many to many
       • where many tables can have many relationships e.g. 1 video can be hired by several customer BUT those customers can hire several videos
     • One to One
       • When one entity can only be related to one entite e.g. 1 man has 1 wife.

2. Vast amounts of info can be stored!

3. Verification

   • Making sure that the data on the source document is the same as the object doucument.
     • Proof Reading- double checking your work basically.
     • Double entry- where two people input the same document or two pieces of the same data are entered and these are then compared any differences are then noted and rectified.

4. Data Validation

   • Makes sure that the data is: accurate sensible,within acceptable boundaries.
     • Length Check
       • Checks that the data entered is a certain length.
     • Lookup
       • Allows only a limited amount of item to be selected
     • Range Check
       • Makes sure that the value entered is between 2 pre-set boundaries
     • Presence Check
       • Makes sure something is entered in the field - cannot be left blank
     • Type Check
       • Makes sure the data entered in the field matches the data type e.g. date/time
   • Validation can be used to reduce errors for data input.
   • Ensures data is present and the correct type, format, range or length.

5. FORMS

   • A window/Screen with multiple spaces to enter data.

6. REPORTS

   • Reports can be created from data stored or queries run
     • presents data taken from a query or from tables in a preformatted attractive manner

7. QUERIES

   • Types
     • Simple- only 1 parameter is used at a time
     • Complex-more than one parameter is used
   • Queries can be run to search for specific records.
     • Parameters can be used they are search criteria

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