In a sense, putting data into a database does the same thing a good accountant does-it organizes a collection of data into information that is useful to those who care about it. E-commerce sites use databases to track their orders and inventory, as well as customer data. The phone company uses databases to track the physical location associated with a particular phone number along with technical information such as the wiring used. Just about every large collection of information in a company is stored in a database. As a result, there are many opportunities for those who create and maintain those databases.
The classic definition of a database states that a database consists of three elements: files, records, and fields. A file can be thought of as a grouped collection of information.The set of your city's White Pages and Yellow Pages can be considered a database, consisting of at least two primary collections of information. The White Pages would be considered a file in this analogy. An example of a record would be your name, address, and phone number entry. Each other person's telephone book entry would be considered a record in the "telephone book" file as well. So, as you can see, a file can contain many hundreds of thousands of records-far more than can be organized and sorted easily by hand. Continuing with this example, there are three individual fields where the various types of information are entered. In this case, the names of the fields are name, address, and phone number. However, a database is not limited to these three fields. In virtually any modern database, fields may be added or subtracted at will, depending on what data the organization needs (or wants) to store. In the case of older databases, a new database sometimes needs to be created, and the previous information imported to the new target database because the structure of some older databases cannot be changed once it is created.
There are two parts to a typical database system: (1) the set of actual data tables and (2) the underlying system software.The software provides the data access language, indexing system, and other utility functions needed to add and delete data from the database and retrieve specific data of interest to the organization.The software is typically bought from a vendor, such as Oracle or Microsoft, and installed by a database or network administrator. The data tables are unique to the organization using the database. Data tables are created by the database designer and are based on input from those who want to access the data. For example, if the organization wants to track phone book entries, they would create a phone book file containing names, addresses, and phone numbers. Once the data files have been defined, it is still necessary to get the actual data records into the database. Two primary means of adding data to a database exist. Adding data can be accomplished by having data entry personnel key records into predefined forms.You can also add data by using automated processes to move data between one database system and another or import it from another organization (an example of this would be the way in which money management programs import your checking account's transaction records into their files from your online banking statement). In either case, a programmer or database designer is involved in designing the automated processes or the data entry forms used to add, display, and change the data.
There are different types of databases, and each major database system software product (such as IBM's DB2) is based on a specific type. Most commonly used are "relational" types of databases. A relational database is one in which the required information is organized into tables, which are related to each other by specific rules established during the design of the database. Most databases in use today, such as SQL Server, DB2, and Oracle, are relational. So, it is important for those in the database field to be familiar with relational database terminology and concepts.
Recently, the database world has emphasized a particular type of database known as a relational database management system (RDBMS). In an RDBMS, a file is known as a table, and a database is considered to be a collection of these tables. A record in a table is known as a row. A field of a table is known as a column. These terms clearly describe the concept of a database to most people because in any sort of written table, such as a transit schedule, people can easily see the table's actual rows and columns. The way in which that table is implemented in a relational database is sometimes as simple as making the table's column headings into the names of fields in the table, and then adding each row of the written table to the database table as data.
Because not all databases are relational databases, the terms file, record, and field are still in common use today. Network, hierarchical, and object-oriented database structures, or organizations, also exist. These are in less frequent use than relational databases due in part to the wide industry acceptance of relational database system software, the excellent tools available for accessing relational database data, and the convenience for database designers and programmers to think about data in a relational way, which is as flat tables of data linked to each other. In particular, hierarchical database organization is becoming popular again. XML (extendable Markup Language) data exchanged across the Internet is structured in a manner that many call a hierarchical database format. This format consists of a master record, such as a purchase order, containing multiple subrecords for ordered items within it.
You may have seen actual databases in use in a variety of places. For example, in a small office, you have probably seen databases created with Microsoft Access.These databases usually keep track of items such as records, accounts, and even names, phone numbers, and addresses. Simply put, databases of any sort contain data. Whether or not you've seen an actual database, you've probably seen information being retrieved from databases many times. If you've visited an airport recently, you've seen the contents of the airport's Arrivals and Departures database displayed on the video monitors throughout the terminal.Your grocery sales slip contains information from a database as well. It is through a database that the barcodes on your groceries are automatically translated into the product descriptions and prices printed on the sales slip. The reality is that there are many varying uses of a database, depending on both user and end user needs.
