Databases

Databases

1. Validation checks

   • Presence Check
     • Used to check that the user enters data into a field and doesn't allow the user to leave an empty field .
     • Its important beacuse it ensures that the data is complete eg: the customer records
   • Type check
     • Ensures that the user can only enter a certain type of data like integer for age and string for name.
   • Range check
     • These are used to limit the range of data a user can enter eg: "1" to "31" for days in a month.
   • Length checks
     • Makes sure that a piece of data is an exact length or doesn't go over a certain amount of characters eg: telephone numbers should only have 11 characters.
   • Lookup
     • Creates a drop down list using a data set.
     • It forces the user to select the data from a drop down list.
   • Input masks
     • Used to make sure that the user enters data in a certain format.
   • Check digits

2. Data types

   • String
     • Characters and symbols
   • Boolean
     • Yes or NO
   • Integer
     • Whole numbers
   • Real
     • Decimals

3. Entitly

   • Is a real world object eg: a database table

4. Attribute

   • The items which make up an entity eg: a field in a database table.

5. Relational Databse

6. Primary Key

   • Is a unique attribute

7. Foreign Key

   • An attribute from another table that is used to link to another entity to reduce data redundancy.
     • Data redundancy is data that is no longer needed(outdated) or repeated data.

8. DBMS

   • Database management system.
   • User interfaces(forms)
   • Run queries
   • Manage record in the table
   • Benefits
     • Easier to maintain/keep secure
     • Database is safe from corruption
     • Multiple people can access it.
     • Can be accessed in multiple ways(tablet,phones,web).
       • Doesn't disrupt if one application is updated.
   • Validation data
   • Integrity Checks