Database: academic
Question: return me the number of organizations in Databases area located in " North America " .
SQL:
SELECT COUNT ( DISTINCT t2.name ) FROM domain_author AS t4 JOIN author AS t1 ON t4.aid  =  t1.aid JOIN DOMAIN AS t3 ON t3.did  =  t4.did JOIN organization AS t2 ON t2.oid  =  t1.oid WHERE t3.name  =  "Databases" AND t2.continent  =  "North America";