CREATE TABLE table_203_385 (id NUMBER, "material" CLOB, "formula" CLOB, "refractive\ index ( es ) \ 589.3 nm" CLOB, "dispersion\ 431 - 687 nm" NUMBER, "hardness\ ( mohs'\ scale ) " CLOB, "density\ ( g/cm3 ) " CLOB, "thermal\ cond." CLOB, "state of\ the art" CLOB)

what 's the difference between the hardness of diamond and the hardness of white sapphire ?
SELECT (SELECT "hardness\n(mohs'\nscale)" FROM table_203_385 WHERE "material" = 'diamond') - (SELECT "hardness\n(mohs'\nscale)" FROM table_203_385 WHERE "material" = 'white sapphire')
SELECT (SELECT "hardness\n(mohs'\nscale)" FROM "table_203_385" WHERE "material" = 'diamond') - (SELECT "hardness\n(mohs'\nscale)" FROM "table_203_385" WHERE "material" = 'white sapphire')