AQA Computer Science GCSE
Databases are only useful if we can search them and extract information from them. That's where a query language comes in.
Query languages are used to search databases - as well as to do other useful things to them.
The main query language is Structured Query Language - or SQL.
Using SQL online
There are various places that you can use SQL online.
> SQLite online - this is my usual option.
To use an online tool you first need to create a database. I'll provide text files of SQL commands that will do this for you - all you need to do is copy and paste the text in and run the commands.
DROP TABLE demo;That should work to remove the demo table.
On the grounds that websites change and school networks block things, two alternaives are:
> SQLite browser from Extend Class
> Online SQLite Compiler - from Coding Ground
Basic SQL Commands
Once you've got the idea of simple databases, we can get more complex...
SQL basics - slides from class
When you're working through the commands, you'd be best off trying them out using SQLite Browser. To do that, you'll need code to create a simple relational database.
Food database code - copy and paste the code
There are four basic commands you need to be able to use:
The syntax rules in SQL aren't that bad, but it's worth having a reminder:
Food database tasks
Food database tables - with some standard questions
Food database tasks - a whole pile of SQL tasks to try out
Use the database creation code that's further up the page to create this database in SQLite.
Some exam style tasks for a simple relational database.
Here's the database creation code so that you can try it out in SQLite.
Airports database code - copy and paste the code
Some other simple relational databases to work with:
Games cafe database code - copy and paste the code