Types of databases

Databases in weights and measures

Database software for home, garden and kitchen use such as MS Access or Filemaker Pro, for example, provide a user-friendly interface for CRUD commands. However, MS Access databases can also be used for database storage behind enterprise software programmed, for example, in Visual Basic or Visual C++.  

Big applications that need to be able to handle a lot of data naturally require corresponding database systems. On Web sites, the database MySQL is the big number one. The database system is open source and free to use. Very large applications such as ERP software can use MySQL or an ORACLE DATABASE. 

Databases can also collect information in an automated fashion. In a number of cases, this raises serious questions about privacy violations. The USA, Britain, Canada, Australia and New Zealand eavesdrop on communication channels worldwide through the ECHELON spy network. The marketing company Doubleclick tries to find out which e-mail addresses are hidden behind IP addresses. For companies, such data are worth a lot of money.  

Databases without relationships 

RDBMS databases are not the only kind of database. There are many other ways to store data. There are NoSQL databases, graphical databases, etc.

Not all databases benefit from a relational structure. After all, the fixed table and column structure makes it difficult to "scale" a database. 

  An example: suppose you create a database listing all ingredients in all possible food products. How do you start that with a classical relational database? Or you want to analyze clickstreams on a website. Not every web page has the same number of links on which the user can click and not every user behaves identically.  Sometimes the fixed structure of the database is not convenient and you feel the need to add more fields or columns. 

In addition, "ACID" is less relevant in such cases. For the clickstreams example: if you miss a few clicks, there are no serious consequences.   In cases like this, companies are increasingly using so-called NoSQL databases. Don't misunderstand. The "No" does not mean that this type of database is "anti-sql." "No" stands for "Not Only SQL." "Well-known examples are: digg, Twitter (both from MySQL to Cassandra) LinkedIn (from Oracle and MySQL to Voldemort), Craigslist (from MySQL to MongoDB) and, of course, Facebook (from MySQL to HBase)."