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Category: Computers & Technology : Programming
Obviously an article such as this won't prepare you for a career as a Database Administrator, but hopefully it will give you the basics on the world of databases and SQL, the main language used to access professional databases. There are many sources on the web for the specifics, but you'll be better prepared to deal with the range of sources (a common problem on the web) after reading this.
Databases are just places to store information in an organized fashion. You could call Excel a database or even an organized set of text documents. However, one will notice that if you want to do complex searches for data in Excel, it is both slow and cumbersome. As such, relational databases were born which optimize search capabilities as well as provide a standard interface.
Databases hold things in tables which are similar to spreadsheets. Tables have fields (or columns) which hold data in rows. You first define your table (ie. My customer table will have fields called name, address, and phone number.), say what type of fields they are (name will be a bunch of letters/numbers, as will address, and phone number will be a set of 7 numbers), then you add data.
Relational databases have special support for multiple tables. If each customer has a bunch of suppliers you want to keep track of, then you'd have a table called suppliers and one of the fields on this table would be a link to the customer table, perhaps name, so that you could relate the tables, hence the name relational database.
SQL (short for structured query language) is a standard way of talking to these databases. This standard aids programmers who use multiple databases. So if I want to get all supplier information of customers whose name is bob, then I'd write "select * (wild card character) from supplierstable where customer_name ='bob'" or to show you the power of the language, if the state was to be changed to Oklahoma in all phone numbers of bob's suppliers, I could write something like "update supplierstable set state = Oklahoma where customer_name = bob" You can get more and more complex, especially with more tables. Again, there are many sources on the web for SQL (try developer.com or cnet.com), but this should give you an idea. One thing to remember is that there are slight variations from DB to DB, so try to get an SQL reference specific to your DB, once you have the basic commands down (select, insert, delete, update, create).
Of course, you can't just type these statements into word and drag them onto a database file. Most of the time, you interface relational databases through a programming language. Languages such as Powerbuilder and Visual Basic were designed with this in mind. Almost all languages support database access and you only need to get the right drivers and connection parameters. After you have connected, you'll send statements like the above (select) and deal with the results, perhaps throwing up nice user friendly windows and buttons for the user to interface with. Microsoft Access is a special case in that it is both a programming language for designing an interface and it is also the database itself, so it is good for beginners and small databases. Most large companies use databases like Oracle, Sybase, or MS SQL Server as they are much faster when dealing with large amounts of data.
As a final word, if you are looking to get into the computer programming profession, it is definitely worth knowing database technology. SQL is very entrenched and knowing it and the basics of how to structure a professional database will make you a valuable commodity for years on end. I found that after only a year of programming Powerbuilder, using SQL to access various back end databases, I could basically pick and choose among jobs.
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