SQL Demystified


Databases contain all different kinds of information. The booking system at an airport might be a database containing all the ticket information for a particular airline, for example.

When the clerk at the check-in desk checks a passenger in for a flight they might enter the passengers name into the computer.In the background SQL is at work.SQL is a computer language which is used to extract information from and put information into databases.So the clerk enters the passengers name, Johnson, into the computer.The computer sends a query to the database using SQL.

The query might look like this:
SELECT * FROM People WHERE Surname='Johnson'

The SQL query is asking the database, to return all the records in the database for people with the surname Johnson.
The database might return the following records:
Johnson, PaulJohnson, MaryJohnson, Matthew

SQL can be used to extract information from a database, add data, modify data and so on.The reason we use SQL is that we need some kind of language to go between the interface and the database.In my exampke, the interface is the screen the clerk uses to check-in passengers and the database contains all of the customer records.So SQL works between these to extract, modify or add records to and from the database.

When you use Yahoo Mail(say for eg), something like SQL is working in the background to update this web site.I hope my example has given you some ideas for further research and explained what SQL is used for.


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