CREATE TABLE table_203_621 (id NUMBER, "player" CLOB, "games played" NUMBER, "minutes played" NUMBER, "minutes played per game" NUMBER, "rebounds" NUMBER, "rebounds per game" NUMBER, "assists" NUMBER, "assists per game" NUMBER, "field goal %" NUMBER, "free throw %" NUMBER, "3-point %" NUMBER, "points" NUMBER, "points per game" NUMBER)

how many more games did allan houston play than mark jackson ?
SELECT (SELECT "games played" FROM table_203_621 WHERE "player" = 'allan houston') - (SELECT "games played" FROM table_203_621 WHERE "player" = 'mark jackson')
SELECT (SELECT "games played" FROM "table_203_621" WHERE "player" = 'allan houston') - (SELECT "games played" FROM "table_203_621" WHERE "player" = 'mark jackson')