CREATE TABLE table_203_56 (id NUMBER, "star" CLOB, "start\ year" NUMBER, "end\ year" NUMBER, "maximum\ year" NUMBER, "maximum\ magnitude" NUMBER, "distance at\ maximum  ( ly ) " NUMBER, "current\ distance" NUMBER, "current\ magnitude" NUMBER)

how much farther -lrb- in ly -rrb- is epsilon canis majoris than zeta sagittarii ?
SELECT (SELECT "distance at\nmaximum (ly)" FROM table_203_56 WHERE "star" = 'epsilon canis majoris') - (SELECT "distance at\nmaximum (ly)" FROM table_203_56 WHERE "star" = 'zeta sagittarii')
SELECT (SELECT "distance at\nmaximum (ly)" FROM "table_203_56" WHERE "star" = 'epsilon canis majoris') - (SELECT "distance at\nmaximum (ly)" FROM "table_203_56" WHERE "star" = 'zeta sagittarii')