CREATE TABLE table_203_526 (id DECIMAL, "team 1" TEXT, "agg." TEXT, "team 2" TEXT, "1st leg" TEXT, "2nd leg" TEXT)

what was the difference in the first and second leg for belgium ?
SELECT (SELECT "1st leg" FROM table_203_526 WHERE "team 2" = 'belgium') - (SELECT "2nd leg" FROM table_203_526 WHERE "team 2" = 'belgium')
SELECT (SELECT "1st leg" FROM "table_203_526" WHERE "team 2" = 'belgium') - (SELECT "2nd leg" FROM "table_203_526" WHERE "team 2" = 'belgium')