hi, can anyone tell me how to calculate the average of data retrieves from a database. The situation is I have a table "number" which consist of several data like "2,5,4,8,6...." I want to calculate the average and display it on the browser. thanks in advance for your help.
< removed >

It's very simple, when selecting data from a table with a query, such as:
SELECT ages FROM buildings WHERE town = 'london'

If you wanted the average of all those ages you do:
SELECT AVG(ages) FROM buildings WHERE town = 'london'

Note that this will return one row, I think. Not one for every building in London that the database stores >_< like the first query would. I am not sure what happens if you mix an average in with a normal one.

Originally Posted by Bozebo

Note that this will return one row, I think. Not one for every building in London that the database stores >_< like the first query would. I am not sure what happens if you mix an average in with a normal one.

Although I don't think the OP wanted to know this, it is possible to mix composite queries (e.g. average or count) with 'normal' queries in a couple of ways:

• Joins (left, right, etc...) via GROUP BY
• Subqueries, where the result of one query is passed to the parent query

SQL optimization can be really interesting. If you really want to know more though you might want to try the MySQL (or MSSQL, though I've never been) support forums - they're full of interesting snibbets like these.
Regards,
Tom