SQL Help - pull URL with specific querystrings

[alagiriv]

Consider we have the following URLs

http://abc.com/?a=1&b=2&c=3
http://abc.com/?d=1&e=2&a=3
http://abc.com/?f=1&g=2&h=3
http://abc.com/?C=1&b=2&a=3

I need to pull all URLs with the querystring that have a= OR b=

output should be like this:

http://abc.com/?a=1&b=2&c=3
http://abc.com/?d=1&e=2&a=3
http://abc.com/?C=1&b=2&a=3

I'm new to Splunk, your input would be of great help.

Thanks,