Solr Query

default for all *:*, : used to separate parameters and values,e.g.

keywords:web

Using AND (&&), OR

content: OWL OR title: Semantic Web
content: OWL && title: Semantic Web
content: OWL AND title: Semantic Web

Nested Queries

using _query_

content:"semantic" AND _query_:"alcategory:computer_internet" AND _query_:"title:web" AND _query_:"keywords:data"

source: http://searchhub.org/dev/2009/03/31/nested-queries-in-solr/