CREATE TABLE teachers (lastname CLOB, firstname CLOB, classroom NUMBER)
CREATE TABLE list (lastname CLOB, firstname CLOB, grade NUMBER, classroom NUMBER)

What are the first names of the teachers who teach grade 1?
SELECT DISTINCT T2.firstname FROM list AS T1 JOIN teachers AS T2 ON T1.classroom = T2.classroom WHERE grade = 1
SELECT DISTINCT "T2"."firstname" FROM "list" "T1" JOIN "teachers" "T2" ON "T1"."classroom" = "T2"."classroom" WHERE "grade" = 1