Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_203_630 ( id number, "rank" number, "nation" text, "gold" number, "silver" number, "bronze" number, "total" number )

### Question ###
south korea has how many more medals that north korea ?

### Accurate SQL ###

SELECT (SELECT "total" FROM table_203_630 WHERE "nation" = 'south korea') - (SELECT "total" FROM table_203_630 WHERE "nation" = 'north korea')