Database: student_transcripts_tracking
Question: What is the id of the semester that had both Masters and Bachelors students enrolled?
SQL: select distinct t2.semester_id from degree_programs as t1 join student_enrolment as t2 on t1.degree_program_id  =  t2.degree_program_id where degree_summary_name  =  'master' intersect select distinct t2.semester_id from degree_programs as t1 join student_enrolment as t2 on t1.degree_program_id  =  t2.degree_program_id where degree_summary_name  =  'bachelor'