[SOLVED] Really Basic Maths Question

[herghost]

Hi all,

 

never dealt with maths before so back to school for I have me!

 

I have a table with an int number, how do I go about subtracting one from this and updating the database?

 

Also is there any good guides on this stuff?

 

Many Thanks!

 

[Mark Baker]

UPDATE table

  SET field=field-1

WHERE condition

[Maq]

This can all be done in MySQL.

 

i.e.

UPDATE [table] SET [field] = [field] - 1;

 

If you don't have a PHP Math question I'm going to move this to the MySQL Help section.

[herghost]

hi, I am not sure how to write this query:

 

$query = 'UPDATE users_credits SET credits = credits - 1 WHERE username = $username';

 

This does not change it!

[Maq]

Variables don't interpolate in single quoted strings.  You should use double quotes for your string and single quotes for your string values.

 

$query = "UPDATE users_credits SET credits = credits - 1 WHERE username = '$username'";

 

A good technique to learn is echoing your query string ($query) to see what you're actually passing.

[herghost]

Thanks Maq

 

Why is it that everytime you think you know a bit, you can never do what you think you can do

[Maq]

Thanks Maq

 

Why is it that everytime you think you know a bit, you can never do what you think you can do

 

Welcome, heh, don't worry it happens to all of us.