A Gramps exporter has been developed in trunk/src/plugins/export/ExportSql.py You can export all of the Gramps genealogical data through an SQL Export using the Export Assistant. This does not export other Gramps data, such as bookmarks, researcher information, etc.
SQL stands for "Structured Query Language" and is pronounced "sequel" (it is a joke: as it came after QUEL, it is its sequel). After you export your GRAMPS data into a file such as Untitled_1.sql using the above Exporter, then you can use SQL queries like:
$ sqlite3 Untitled_1.sql SQLite version 3.5.9 Enter ".help" for instructions sqlite> .tables dates family names people repository events media notes places sources sqlite> .headers on .headers on sqlite> select * from people; handle|gramps_id|gender|death_ref_index|birth_ref_index|change|marker0|marker1|private b247d7186567ff472ef|I0000|1|-1|-1|1225135132|-1||0 sqlite> select * from names where surname like "%Smith%"; private|first_name|surname|suffix|title|name_type0|name_type1|prefix|patronymic|group_as|sort_as|display_as|call 0|Test|Smith|||2|||||0|0| sqlite> .exit $