CREATE TABLE table_204_649 (id NUMBER, "rank" NUMBER, "name" CLOB, "image" NUMBER, "height\ ft  ( m ) " CLOB, "floors" NUMBER, "year" NUMBER, "notes" CLOB)

what is the difference in height between key tower and 55 public square
SELECT ABS((SELECT "height\nft (m)" FROM table_204_649 WHERE "name" = 'key tower') - (SELECT "height\nft (m)" FROM table_204_649 WHERE "name" = '55 public square'))
SELECT ABS((SELECT "height\nft (m)" FROM "table_204_649" WHERE "name" = 'key tower') - (SELECT "height\nft (m)" FROM "table_204_649" WHERE "name" = '55 public square'))