Speeding Up Queries with Semi-Joins and Anti-Joins: How Oracle Evaluates EXISTS, NOT EXISTS, IN, and NOT INby Roger Schrag Database Specialists, Inc. About Database Specialists, Inc. Database Specialists, Inc. provides remote DBA services and onsite database support for your mission critical Oracle systems. Since 1995, we have been providing Oracle database consulting in Solaris, HP-UX, Linux, A..