14+Database+systems

__ Definition __  __ Database Software __  __ Flat-File Systems __  __ Disadvantages of Flat-File Systems __  __ Differences: Relational Databases & Flat-File Systems __ __ Advantages of Relational Databases __  __ Disadvantages of Relational Databases __  __ Database Security __  __ Hierarchy of Passwords __  __Storage of Data__
 * __ Databases __**
 * Large collection of data items and links between them structured so they can be accessed in applications programs.
 * Software used to manipulate data is the Data Management System.
 * Software that allows for data entry and then stores the data safely.
 * Data management systems keep data separated from the program itself. Data is created first then handled by other software.
 * Businesses tend to use Relational Databases.
 * Relational Databases: Data held in different tables with links (relationships) between them.
 * Is like a computerised card box file to store one record. A single card for one record.
 * A record is the whole information about a product, item or person.
 * An item of data like surname is a field.
 *  Flat-Files contain only one table they are used as purely storage and retrieval facilities.
 * They are not as flexible as Relational Databases so they are ineffectual for business use.
 * The flat-file databases can be generated by spreadsheet software.
 * The same data may be entered twice.
 * Time consuming.
 * One deleted record may take useful data with it.
 * Data is store in one table for Flat-File but multiple tables used for Relational Databases.
 * Relationships (links) used only in the Relational Databases.
 * Data being combined might make it more flexible combinations of information can be simulated.
 * Data is unlikely to be duplicated.
 * Data integrity maintained as updates are easier if entered in one place.
 *  Easier to search for specific data items relational databases have comprehensive search facilities.
 * The application can be built around the database.
 * Relational Databases need to be carefully planned.
 * Relational Databases tend to be more expensive.
 * Relational Databases are ineffective to build simple lists.
 * Password systems are used.
 * People are given access rights which restrict unauthorised users from the databases.
 * Access rights determined by hierarchy of passwords.
 *  Access Rights given so Sales department cannot access the Human Resources department’s files.
 * Database administrator will control the users’ access rights.
 * The higher up the hierarchy the more freedom the user will get.
 *  They can get Access to certain groups of data relevant tot their job.
 *  Senior Mangers can gain have full access to everything.
 *  Stages of user rights could be: read only so the user cannot modify an open document.
 * Another is Read & Write where they can alter data.
 * Execute this could prevent users from copying files altogether.
 * The data is in containment so if applications are changed or updated then the data will remain unchanged and unaffected.