Timestamp updating in table with REPLACE INTO

Question

I have a plus/minus system where a user can add one or minus one away from a blog post.

My database (MySQL) table looks like this: userid entry id vote - which is +1 or -1 timeStamp

I have set the timeStamp to default to CURRENT_TIMESTAMP.

I have to methods plus() and minus(). Both do the same thing but one inserts +1 into 'vote' and the other inserts -1. Since (userid,entryid) is the primary key, I am using REPLACE INTO. INSERT INTO brings up a duplication error. INSERT IGNORE doesn't let the user change the vote from +1 to -1

"REPLACE INTO votes(userid, entryid, vote) VALUES(:uid,:eid, -1)";

Ignore the values..

While REPLACE INTO works perfectly, I am ordering by the timestamp, so when someone clicks +1 a second time after voting, it updates the timestamp, which brings it to the top of the list.

Anyone know a solution to this?

ps sorry for the bad title. Couldn't think of a suitable one.

Answer 1

Using the INSERT ... ON DUPLICATE KEY UPDATE Syntax of MySQL, you could perform the check inline, and only update the timestamp IF the vote actually changed:

INSERT INTO 
  votes 
SET 
  userid = :uid, 
  entryid = :eid, 
  vote = :vote,
  timeStamp = NOW()  /* I'm being explicit here -- you don't need this */
ON DUPLICATE KEY UPDATE 
  vote = :vote, 
  timeStamp = IF(vote = :vote, timeStamp, NOW())