Database

Database

1. Keywords

   • Data redundancy
     • When data is no longer needed. Foreign keys stop this because they stop you from having to repeat the same data twice
   • Entity
     • A real world object. For example, a table
   • Attribute
     • An attribute is a feature that is specific to one Entity. Just like a field in a database.

2. Validation checks

   • Presence check
     • Ensures that the data is complete
   • Input masks
     • Ensures the data entered is in a particular format by defining the valid characters permitted in a field
   • Length check
     • Checks how many characters are in a string. For example, a phone number can only have 11 characters
   • Range checks
     • Limits the range of data by using two values that the range must be between. For example when entering data into the day field it must be an integer between 1 and 31.
   • Type check
     • A type check restricts the data type entered into a field. For example, if an integer was entered into a text field an error message would occur
   • Lookup
     • This restricts the data limit by using a drop-down list so the end user can select an option from a list

3. Data types

   • String
     • Letters
     • Numbers
   • Integer
     • Number
   • Real
     • A decimal number
   • Boolean
     • True / False, Yes/ No, 0/1

4. Flat file vs Relational

   • Flat file
     • A flat file database has a lot of data redundancy because there are no primary or foreign keys
   • Relational
     • A relational database is structured to recognise relations between stored items of information.

5. Primary and foreign keys

   • Primary Key
   • Foreign Keys

6. DBMS

   • Database management system
   • Manages records in a table
   • Run report
   • User interfaces (forms)
   • Run queries
     • >< AND, OR, NOT
   • Benefits
     • Easier to maintain / keep secure
     • Database is safe from corrupt
     • Set up by experts and used by end user
     • Database can be accessed in multiple ways (tablet, pc, web, phone)
       • Doesn't disrupt if the application is updated