2. courses taken by boston residents and tought by assoc Profs

R0 = select city="boston" from students
stno name addr city state zip
2890 mcLane_Sandy 30 Cass Rd boston ma 02122
4022 prior_Lorraine 8 Beacon St boston ma 02125
5544 rawlings_Jerry 15 Pleasant Dr boston ma 02115
R1 = select rank="assoc Prof" on instructors
empno name rank roomno telno
056 sawyer_Kathy assoc_Prof 91 5110
126 davis_William assoc_Prof 72 5411
R2 = rename name to stname in R0
stno stname addr city state zip
2890 mcLane_Sandy 30 Cass Rd boston ma 02122
4022 prior_Lorraine 8 Beacon St boston ma 02125
5544 rawlings_Jerry 15 Pleasant Dr boston ma 02115
R3 = join R1 with R2  
R4 = join R4 with grades
stno empno cno sem year grade name addr city state zip name rank roomno telno
5544 056 cs240 spring 93 70 rawlings_Jerry 15 Pleasant Dr boston ma 02115 sawyer_Kathy assoc_Prof 91 5110
4022 056 cs240 spring 93 80 prior_Lorraine 8 Beacon St boston ma 02125 sawyer_Kathy assoc_Prof 91 5110
R5 = project R4 on cno
cno
cs240
cs240