I spent a lot of time trying to select snippets with
contain multiple tags. (series60 and sql)
There is no '+' links I can click anymore.
After about 10 minutes of trial and error, I find out how.
This also answer another question on correct use of URL.

# for tag 'series60' AND 'sql'
http://www.bigbold.com/snippets/tags/series60/sql/

# this doesn't work
http://www.bigbold.com/snippets/tag/series60/sql/

# all of these work (single tag case)
http://bigbold.com/snippets/tag/series60/
http://bigbold.com/snippets/tags/series60/
http://www.bigbold.com/snippets/tag/series60/
http://www.bigbold.com/snippets/tags/series60/

My conclusion is that.
For a single tag, use '/tag/...'.
For multiple tags, use '/tags/...'.
The first is quicker to type, while the second is flexible in case you want to filter further.

// description of your code here

SELECT fulltxt.pqid AS candidate_ft, citations.chid
FROM citations,fulltxt
WHERE citations.issn = fulltxt.issn
AND citations.volume = fulltxt.volume
AND citations.issue = fulltxt.issue
AND citations.year = fulltxt.year
AND citations.spage = fulltxt.spage
AND citations.pqid = ''
;