Database Revision

Database Revision

1. Definitions

   • Primary keys
     • Unique code or number (Staff ID)
   • Tables
     • Information stored in these- all of the records in a database is stored in a table, usually more than one
   • Record
     • All the information about a person or a thing
   • Field
     • Each record is made up from information called a field (First Name, Last name etc.)
   • Foreign Key
     • How table link together in a relational database. its a foreign key in one table but a primary in another

2. Normalisation

   • Technique for Designing relational database tables to reduce duplication
   • Eliminates redundant data, organises data efficiently, ensures that only related data is in the table
   • Normal Forms
     • 0NF
       • First collect the Data
     • 1NF
       • All data must be atomic (Broken down into different parts)
       • Each field has a unique name
       • No repeating fields in a single record
       • Each table must have a primary key
       • Questions To ask yourself to spot 1NF
         • Does it have a primary key?
         • Are each field name unique?
         • Is the data atomic
         • Are there repeating redundant fields?
     • 2NF
       • Non key attributes must depend on every part of the primary key
       • Table must already be in 1NF
     • 3NF
       • Must be in 2NF
       • Every field has to rely on every other field