CREATE TABLE table_203_530 (id DECIMAL, "country" TEXT, "gdp  ( usd bln ,  2012 ) " DECIMAL, "gdp  ( usd bln ,  2017 ) " DECIMAL, "gdp  ( usd ppp bln ,  2012 ) " DECIMAL, "gdp  ( usd ppp bln ,  2017 ) " DECIMAL, "per capita  ( usd ,  2012 ) " DECIMAL, "per capita  ( usd ,  2017 ) " DECIMAL, "per capita  ( usd ppp ,  2012 ) " DECIMAL, "per capita  ( usd ppp ,  2017 ) " DECIMAL)

what is the difference in the gdp -lrb- usd bin -rrb- in 2012 between algeria and comoros ?
SELECT (SELECT "gdp (usd bln, 2012)" FROM table_203_530 WHERE "country" = 'algeria') - (SELECT "gdp (usd bln, 2012)" FROM table_203_530 WHERE "country" = 'comoros')
SELECT (SELECT "gdp (usd bln, 2012)" FROM "table_203_530" WHERE "country" = 'algeria') - (SELECT "gdp (usd bln, 2012)" FROM "table_203_530" WHERE "country" = 'comoros')