I want to find all the pages with cq:tag which end with "/testingtag"
is it possible to do so using ?
Are there any online tutorial on JCR QueryBuilder?
I tried something like that but unfortunately it is not showing what I expected to see
Note that the querybuilder is a CQ (AEM) specific feature. A google search should give you what you want in the first search results: http://lmgtfy.com/?q=cq+querybuilder
Now regarding your specific question: you want to use the property predicate with the like operation:
However, I don't see why you would want to search for all tags ending with a certain name. Tags must always be present under /etc/tags to be valid and so the logic would always be "let the user search/select some tags, and then search for that list specifically". Use the cq tagging API (javadocs) and also the querybuilder tag predicates (which are unfortunately not so well documented):
tagid.property=jcr:content/cq:tags # to set a different property path; the default is cq:tags
See also http://forums.adobe.com/message/4691188, http://forums.adobe.com/message/5223518 or https://www.sfu.ca/itservices/cms/howto/advanced/organize-and-optimize/advanced-queries.ht ml for some tagid predicate samples.