CREATE TABLE table_8181 ("Player" TEXT, "Nationality" TEXT, "Jersey Number ( s ) " TEXT, "Position" TEXT, "Years" TEXT)

What is Years, when Jersey Number(s) is 21, and when Position is SG?
SELECT "Years" FROM table_8181 WHERE "Jersey Number(s)" = '21' AND "Position" = 'sg'
SELECT "Years" FROM "table_8181" WHERE "Jersey Number(s)" = '21' AND "Position" = 'sg'