November 2008 – The Accidental Developer

Javascript textarea counter

I’ve been thinking more about the textarea counter issue that I mentioned in my previous post (“Users Paste Differently“).

First of all, I noticed that some of the textarea counter scripts date back to at least 2000, so this has been a problem that developers have been looking to solve for 8 years. I checked the HTML 5 specification and found that in HTML 5, the textarea element has a maxlength attribute. Presumably user agents will build in the most elegant solution.

But what is the current most elegant solution? Continue reading Javascript textarea counter

Users Paste Differently

I’ve been using a relatively generic Javascript textarea counter for several years to restrict the input length on form textareas. I’m not sure where the specific version I’m using came from, but you can find dozens like it on Google.

Almost all of them rely on the onKeyDown and onKeyUp events to trigger the script. However, some users still manage to submit text that exceeded the limits, even though the application required Javascript. I could not for the life of me reproduce this issue…until today.
Continue reading Users Paste Differently

Selecting the newest row in one-to-many on mySQL

This one was quite a sticky wicket. So what if you have two tables in mySQL, with a one-to-many relationship (say a forum and comments in that forum), and each of the comments is dated. Now let’s say you want a result set containing each forum’s name, and with it the text of the newest comment in that forum.

The obvious way to do this is with a subselect, which mySQL doesn’t have. So how does one do it?

At first I thought that it might be impossible, but I have figured out the answer:

SELECT f.forum_id,
       max(c.created_on) as last_date,
       c2.created_on as created_on,
       c2.text
FROM   forum f
       LEFT JOIN comment c ON (c.forum_id = f.forum_id)
       LEFT JOIN comment c2 ON (f.forum_id = c2.forum_id)
GROUP BY f.forum_id, c2.comment_id
HAVING created_on = last_date OR last_date IS NULL;

See, it’s pretty clever actually, though it leans on the “HAVING” option, which is sort of crappy. The trick is to join the comment table with the forum table twice. One of those joins gets grouped by forum id so that you can use the max function on it. The other doesn’t get grouped (by adding its primary key to the group by clause) so that you can still pull data out of it. Then you use the having clause to find only the row that has the max date.

I am also accepting values with a max value of NULL so that if a forum has no comments, it still comes back in the results.

Hope this helps someone, somewhere.
Happy Hacking