In the very little spear time that I have, I began learning about databases as they pertain to medical informatics, a field that I am very interested in. So to help me retain what I have learned I am going to write short summaries on what I have learned and post them here.
Database: A Database is any collection of data that stored with a defined structure to serve a purpose. When we use the term database we refer to a computer database, that is a database that is stored on a computer or a series of computers. In order for a computer to create, access or modify the database the computer must first have a Database Management System (DBMS).
Types of Databases
Flat Databases: These databases have the least amount of structure. They are usually a large table with the first row being variable and all the other rows being data. Flat databases are very simple and work efficiently for small portions of data. However they are not able to be tweaked for specialized usage and functionality and they are not conducive to complicated search queries that divide the database further.
Relational Databases: These databases are databases in which records are stored with related fields as data. To effectively store data information items and and their relationships are stored in a table format. The first row of the tables usually belong to the same case and are related. One column of the table is considered the key. Tables in relational databases does not need to be the same size but must all have a key column which connects them to each other. These databases are usually harder to design but makes it easier for the end users.
Hierarchical Databases: These are databases which have sub databases with the same characteristics as the parent database. They are like folders on ones computer. It works as the parent database has children databases within it, if something is modified on the parent the children will be affected too. If the parent is deleted so will the child databases within it. This database type makes it easy to modify databases as a group that should all have the same characteristics maintained.
Distributed Databases: So far all the databases I have mentioned are databases that are created and stored on one computer or server. Distributed databases however are different. Distributed databases are databases in which data is stored on different computers in different settings. One or more computers will contain the index as to where each piece of data is stored, by using the address of the data the DBMS could retrieve and modify the data as needed. One key feature of this type of database is an audit trail. Audit trails are created whenever someone modifies, adds, deletes, or access the data to keep track of who is accessing in or changing it. Therefore a system administrator can know and manage everything that is taking place within the database.
Federated Databases: These operate similarly to distributed databases but have more enhanced security features. Each local database are responsible for managing their own data and security. It is the local database that chooses whether or not to connect to the federation and how they process incoming requests and queries.