CREATE TABLE table_203_539 (id DECIMAL, "year" DECIMAL, "competition" TEXT, "venue" TEXT, "position" TEXT, "event" TEXT, "notes" DECIMAL)

which competition was shi dongpeng in before the world junior championships ?
SELECT "competition" FROM table_203_539 WHERE "year" < (SELECT "year" FROM table_203_539 WHERE "competition" = 'world junior championships') ORDER BY "year" LIMIT 1
SELECT "competition" FROM "table_203_539" WHERE "year" < (SELECT "year" FROM "table_203_539" WHERE "competition" = 'world junior championships') ORDER BY "year" NULLS FIRST LIMIT 1