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_249 ( id number, "position" number, "song title" text, "artist" text, "sales" number, "highest position" number )

### Question ###
what is the difference between the sales of think twice and back for good ?

### Accurate SQL ###

SELECT ABS((SELECT "sales" FROM table_203_249 WHERE "song title" = 'think twice') - (SELECT "sales" FROM table_203_249 WHERE "song title" = 'back for good'))