MySQL ignores UPDATE when data is the same?

[solitario]

Hello all.
I just discovered (correct me if I'm wrong), that MySQL ignores an UPDATE when the data is exactly the same as already in the database.

For instance, I have this query:

UPDATE cms_users SET user_email="[email protected]", internal_notes="blah blah blah" WHERE cms_users.user_id=8

I pass that to a class function which executes the query and returns the number of affected rows:

$affected_rows=$database->execute($query);

Then I was testing it:

/* DETERMINE IF THE QUERY WAS SUCCESSFUL */
	if(
		$affected_rows>0
	) {

		/* SUCCESS */
			/* REDIRECT BY CALLING THE FUNCTION WHICH BUILDS A REDIRECT URL */
				header('Location: '.admin_redirect_url('thank'));

	} else {

		/* FAILURE */
			/* REDIRECT BY CALLING THE FUNCTION WHICH BUILDS A REDIRECT URL */
				header('Location: '.admin_redirect_url('err05'));

	}

Once I actually changed the data, the value returned by the class function went from 0 to 1.

So my questions are:
1) is it MySQL or PHP which is doing this?
2) is there a way of "forcing" the database to update, without say, adding a timestamp?

Many thanks.

[kows]

I'm not sure of an easy way to check, but I would think that MySQL itself would not bother updating a record that had the same value. MySQL would do it all internally, whereas PHP is just being passed an SQL query and is sending it to MySQL. For PHP to do this check, it seems like it would be -very- inefficient. I doubt there's any way of forcing it to update, either. There's no point in MySQL updating a record if there is nothing to update ;)

From the looks of it, you're just checking to see if your query was successful. Don't use mysql_affected_rows(), and instead just do:

if(mysql_query("UPDATE table SET field='value' WHERE field2='value2' LIMIT 1")){
  //success
}else{
  //failure
} 

It should produce the result you're looking for.

[solitario]

Thanks kows.

Just found this at the MySQL site:
"If you set a column to the value it currently has, MySQL notices this and does not update it."

I could write another class function, as you describe, which returns a boolean upon success/failure. I guess I was just being lazy and trying to use the same function for multiple purposes. Thanks.