CREATE TABLE purchase (member_id VARCHAR)
CREATE TABLE member (member_id VARCHAR, level VARCHAR)

What is the total number of purchases for members with level 6?
SELECT COUNT(*) FROM purchase AS T1 JOIN member AS T2 ON T1.member_id = T2.member_id WHERE T2.level = 6
SELECT COUNT(*) FROM "purchase" AS "T1" JOIN "member" AS "T2" ON "T1"."member_id" = "T2"."member_id" AND "T2"."level" = 6