Question: I've been searching for a solution to this, which I thought would be trivial, and seems pretty much impossible. 

Here's the situation: I set up an AdWords campaign, ad groups and ads. I point them to www.mysite.com 

Once visitors arrive to my site through one of my ads, I want to know which exact ad they clicked on (and campaign, as apparently the ad id isn't globally unqiue). Is this possible?

I first tried by enabling Destination URL auto-tagging, but seems like the gclid parameter is pretty much useless.

Then I looked at the UTMZ cookie, but it seems like at most (correct me if this isn't the case), you get the campaign number (is this even the ID in AdWords?) and the keywords searched or the ad's keywords, one of those. Not anything I can uniquely identify the ad by, right?

Finally, I looked at ValueTrack, although again correct me if I'm wrong, but this would mean manually changing the destination URL of each of my ads in AdWords, right? Even doing this, I'm not sure I can get something that lets me uniquely identify the clicked ad. Is {creative} what I want? It's described in the docs as the "unique ID of the creative", does that mean this includes the Campaign.Id and the AdGroupAd.Id?

Thanks!

Answer: 
As far as I know there is no value track for campaign or ad group ID. You could just append something to the end of each ad's destination URL based on the campaign & ad group, but that is a bit of a chore.

If you [link your Google Analytics & AdWords accounts](https://support.google.com/adwords/answer/1704341?hl=en-GB) and use auto-tagging in AdWords you can get the information you want in GA through the AdWords report (shows campaign, ad group, keyword etc). GA is able to use the gclid to retrieve data from AdWords, and I think you can then use the GA API to get the campaign data back out if you want it.
You can get this data from the CLICK\_PERFORMANCE\_REPORT - The only downside to this, is that this report can only be run for 1 day. so if you needed a month worth of data - you would have to run about 30 reports - 

The ad Id is the "CreativeId" - you can get the campaignId and Adgroup ID as well from this report - there is 1 row for each click - (GCLID) these are unique. 

see this link for more info on what fields are available 

<https://developers.google.com/adwords/api/docs/appendix/reports#click>