Database Management Systems
Database Concepts

Database management systems(DBMS)- are collections of tools used to manage databases. Four basic functions performed by all DBMS are:
  * Create, modify, and delete data structures, e.g. tables
  * Add, modify, and delete data
  * Retrieve data selectively
  * Generate reports based on data

A short list of database applications would include:
  * Inventory
  * Payroll
  * Membership
  * Orders
  * Shipping
  * Reservation
  * Invoicing
  * Accounting
  * Security
  * Catalogues
  * Mailing
  * Medical records

Database Components
Looking from the top down, databases are composed of related tables, which in turn are composed of fields and records.

A field is an area (within a record) reserved for a specific piece of data. Examples: customer number, customer name, street address, city, state, phone, current balance.

Fields are defined by:

  * Field name
  * Data type
Character: text, including such things as telephone numbers and zip codes
Numeric: numbers which can be manipulated using math operators
Date: calendar dates which can be manipulated mathematically
Logical: True or False, Yes or No
  * Field size
Amount of space reserved for storing data

A record is the collection of values for all the fields pertaining to one entity: i.e. a person, product, company, transaction, etc.

A table is a collection of related records. For example, employee table, product table, customer, and orders tables.
In a table, records are represented by rows and fields are represented as columns.

A database is a collection of related tables. It can also include other objects, such as queries, forms, and reports. The structure of a database is the relationships between its tables.

There are three types of relationships which can exist between tables:
The most common...