I know you can select a tag and then click on unanswered to view the unanswered questions for that tag.
But is there a way to view questions only for a certain set of tags > 1 tag?
Mainly I'd like the union of tag1 with tag2 with tag3 with tag4.
But also the intersection of tags would be nice as well.
If you click on a tag, you get a listing of questions in that tag. In this listing, if you click on a tag in the “Related Tags” box on the right, you get a view of questions that have both the tag you originally selected and the second tag you clicked on, i.e. you get questions with tag1 and tag2 (intersection). You can repeat to get questions with tag1 and tag2 and tag3, and so on. For example, from questions tagged etymology on English Language & Usage, click on [idioms] to get questions with both the etymology and idioms tags.
Only the most common tags appear in the “Related Tags” box. You can also type tags manually in the search box. If you type [tag1] [tag2] (tag names in square brackets), you get the questions tagged with tag1 and tag2, and so on. For example, from questions tagged etymology on English Language & Usage, add [metaphors] in the search box to see questions with both the etymology and metaphors tags.
You can get a listing of questions that have tag1 or tag2 (union) by typing [tag1] or [tag2] in the search box. For example, from questions tagged etymology on English Language & Usage, add or [history] in the search box to see questions with either the etymology or the history tag.
You can also use a wildcard character: to list all questions with a tag that begins with a certain prefix, type [prefix*] in the search bo. For example, typing [gramm*] in the search box on English Language & Usage redirects to questions tagged grammar or grammaticality or grammatical-number or grammatical-structure or grammatically or grammatical-gender.
You can omit questions with a certain tag by typing -[boring-tag] in the search box. This can be combined with multiple tags: [tag1] [tag2] -[boring-tag] lists questions that have both tag1 and tag2 but not boring-tag. For example, from questions tagged slang on English Language & Usage, add -[offensive-language] in the search box to see questions tagged slang but not offensive-language.
I would like the filtering to support NOT also. Since there are so many tags and some might be duplicate/similar items. It might be easier to filter out that I know that I'm not interested in seeing, so I can still see questions that might interest me. If later I found out I'm not interested in it, I can always add it into the filter list.
For example, I am mostly into Java, Ruby, design, etc. If I only filter on those then I might miss out on interesting questions on C#, Scala, or F#. But I might be interested with C# only on the language aspect, but not interested in API specific questions like WCF. If it supports a NOT filter, then I can just filter out WPF and still catch interesting C# questions without being drown by all the questions that show up here.
I remembered the intersection of tags from listening to the podcast...
Use a space between each tag (or %20). Example for tags c++ and c#:
http://beta.stackoverflow.com/questions/tagged/c++%20c%23
Not sure about the union of tags though.
I've written a very rough Greasemonkey script that will filter tags by ORing them.
No warranties are expressed or implied, your mileage may vary, etc. Currently, you have to edit the favourite_tags variable to specify your favourite tags.
Also, it just hides things from the current page, so if you're viewing 10 items at a time and only three match, it'll just show you three - it won't (yet!) cycle through the pages until you get 10 hits. For this reason, it's probably only useful if you do an awful lot of "any new questions that I can answer" checking, but this is similar to @Brian R. Bondy's question.
In the search box enter tags between sqeare brakets. However you still need at least one keyword or it won't work. eg this will pick up this post, since its the only one with all 3 tags
[stackoverflow] [tags] [tagging] view
EDIT:
"multiple tags on tag page"
Link
Admin response
as of tonight's push you can search tags by adding them in brackets eg [java] [sql]
I'm pretty sure they mentioned more extensive tag filtering as being a "maybe next release" feature. Ask on UserVoice.
I would also like an OR function - I think this is a very common use as people will want to watch for questions & answers of interest and generally people are interested in more than one tag!
You can edit the link and provide my tags by separating them with space, err, that is, separating them by %20, which is the URL encoding for a space.
So, the URL to look at C# questions is:
http://beta.stackoverflow.com/questions/tagged/c%23
If you want to get all questions about C# and SQL, you can modify it to this:
http://beta.stackoverflow.com/questions/tagged/c%23%20SQL
This will give you the intersection query. There is, AFAIK, no way to do a union query as of yet. I'm sure they'll provide one eventually.