Databases are one of the most important reasons for the development and advancement of information systems. There are many database types. These are methodologies for organizing and arranging databases to facilitate and accelerate searches and access to stored data. Some are traditional and some are modern, but in both cases, the programmer must have information about what has been and what is now.
These data scattered in the shelves and papers that fill the libraries and stores represent manual databases, and because of this hash came important and logical classifications to classify the data according to their relationship to each other or according to mathematical or logical structure, and based on what I mentioned to you are considered files stored in the shelves and sales invoices scheduled Electronically and the addresses of people in a document file are examples of manual data.
This type of database is one of the most used by human beings for coordinating information. It is one of the ways that the human mind uses a lot in attempts to remember old events. A simple relationship can make you remember big events.
This type of database has good features, such as entering data only once, there is no need to duplicate, and small tables can be created and modified easily, the small clear relationship is easier to modify, in addition to the possibility of adding tables to the database in any time.
In this system, a large table containing all data is created. As if all the information you have in a single sheet.
It is no secret to you the strangeness of this method and may have imagined several disadvantages, in this type of databases are repeated data frequently, if you enter a product 10 times will write the phone number of the supplier, for example, 10 times as well !! It does not hide when you amend the number will be adjusted as well as 10 times as well.
This rule is based on the principle of the hierarchy at work, as it does a sequence of origin, or root, as this system begins to branch in the form of sections, and the principle of its work to access data in a sequential and branched, and be either from the bottom up or from Top to bottom.
This type of database emerged at the time of the popularity of databases hierarchical form, hierarchical form depends on the father is single and have several children, but it was found that some data are linked in a way several children with several parents and vice versa. Perhaps it does not make sense to have multiple parents in fact, but in databases, it happens.
Types IV and V are limited to large needs because they usually require large-scale memories. However, they have many advantages, they are more efficient than relational databases and deal with a very large amount of information, in addition to providing based on the way the files are organized by large areas of the storage database.