What is a Database
Definition: A database is a structured collection of records or data.
Many moons ago, I was shown an database that was constructed back in the 50s. It was hand held and consisted of a stack of cards that contained information about plant biology. There was a series of holes that wrapped around the cards, some of the holes were notches, and others were not.
To query the database, one placed a pin through one of the wholes and let the cards that had a notch fall out of the stack. You could continue this process by removing and adding pins to select different combinations of data.
Once you had narrowed your search, you could read the cards, and retrieve the data.
This was a very manual process, and I doubt that anyone today would take the time to learn to use such a tool, let alone update or add records to it.
More Modern Databases
Replacing Card Catalogues in libraries, Rolodex on desktops, and filing rooms in offices, is our new electronic concept of databases. At a rudimentary level, and fitting under the definition of the database that we started with fall many simple documents.
A post-it note is not a database, but a list of names and numbers on a contact list is. It has regular structure, and the data can be retrieved using a routine. And this is as far as most people need to go. They see databases like spreadsheets. They even use filters and link cells for calculations.
More than just a list
A database that just holds a list of records is a single table Database. This is like a spreadsheet and the only real advantage is that Databases on computers are generally designed to be queried by other applications. The contact list in your email client is not much more than a flat table. But it is queried and updated from the email application. This makes the application more useful.
Database Normalization explained.
Again, long ago, I had a watch that held phone numbers. This worked pretty well, and had an alpha-numeric keyboard. But the data was in a silo. There was no way to get the data in or out other than the small screen and keypad. Application bound, embedded databases are also silos of data.
Many applications now use, or have the option to use, an embedded database. But databases that can be used by more than one application, and are treated like an object are even more useful. When a database is shared between applications, we can gain exponential utility. Every new application that can query the shared database becomes more efficient.
RDBMS More than a single table.
One of the things that we will discuss more later, is the concept of a relational database. What this means is that we have more than one table, that have related fields. A analogous example is the an email system with an integrated calender. Now we have the schema or table that contains the contact and relate them to people invited to the events. These systems have been around for quite a while and gives us a conceptual model of how related tables bring power to a Relational Database Management System (RDBMS).
Data in a Hierarchy
RDBMS is not the only way to organize data. One way that some databases organize data is in a hierarchical schema. In this fashion instead of tables, we have a conceptual model like a directory tree. Data is located in a name space that is organized like files in directories. Data in this type of structure gains some implicit structure and relationship as a parent child relationships exists in the data naturally. For small sets of data this can make the database small and fast. However the ability to build abstract structures, relationships and queries are more difficult with this structure, and the database really grows when extended to cover the features of multiple relational data reference.
All Shapes and Sizes
More basic than the most simple table or hierarchy based database is the file based system. This is really what it sounds like. A simple text file or an XML file can be used as a database. These can support queries, inserts and joins. Even though the database is in a standard file that can be opened and accessed with a common text editor, it has a structure and can be used to keep the application data organized.
Databases for the Integration Engineer
As integration Engineers, we will sometimes find ourselves working directly with and application’s database. Sometimes this database will be a full blown enterprise level database implementation. Many times, however, it will be something more simple like an embedded table or xml file that the application treats as its database. Whatever the case, we need to learn and respect the structure of the data, and work to ensure that our integration preserves the integrity of the data structure.
