select ad_group_ad.ad.type, ad_group_ad.ad_group, ad_group_ad.ad.id, ad_group_ad.ad.url_custom_parameters, ad_group_ad.status, ad_group_ad.ad.final_urls
from ad_group_ad where campaign.id = #######
```
In this case, `ad_group_ad.ad.final_urls` comes back as a list of strings, but so far I've not gotten anything back for ad_group_ad.ad.url_custom_parameters
Side beef: I tried many incantations for the `where` clause and kept getting internal errors from google. I tried `ad_group.campaign = resource_name,
ad_group.campaign.resource_name, ad_group_ad.campaign.resource_name` and kept getting completely unhelpful internal errors.