CREATE TABLE trained_in (physician VARCHAR2, treatment VARCHAR2)
CREATE TABLE physician (employeeid VARCHAR2, name VARCHAR2)
CREATE TABLE procedures (cost NUMBER, code VARCHAR2)

What is the average cost of procedures that physician John Wen was trained in?
SELECT AVG(T3.cost) FROM physician AS T1 JOIN trained_in AS T2 ON T1.employeeid = T2.physician JOIN procedures AS T3 ON T3.code = T2.treatment WHERE T1.name = "John Wen"
SELECT AVG("T3"."cost") FROM "physician" "T1" JOIN "trained_in" "T2" ON "T1"."employeeid" = "T2"."physician" JOIN "procedures" "T3" ON "T2"."treatment" = "T3"."code" WHERE "John Wen" = "T1"."name"