CREATE TABLE course (course_id VARCHAR, title VARCHAR)
CREATE TABLE teaches (id VARCHAR, course_id VARCHAR)
CREATE TABLE instructor (name VARCHAR, id VARCHAR)

Find the name of the instructors who taught C Programming course before.
SELECT T1.name FROM instructor AS T1 JOIN teaches AS T2 ON T1.id = T2.id JOIN course AS T3 ON T2.course_id = T3.course_id WHERE T3.title = 'C Programming'
SELECT "T1"."name" FROM "instructor" AS "T1" JOIN "teaches" AS "T2" ON "T1"."id" = "T2"."id" JOIN "course" AS "T3" ON "T2"."course_id" = "T3"."course_id" AND "T3"."title" = 'C Programming'