explain Select DURATION, Case WHEN TO_NUMBER(REGEXP_REPLACE(DURATION, '[^0-9] ', '')) <= 3 THEN 'Short' WHEN TO_NUMBER(REGEXP_REPLACE(DURATION, '[^0-9] ', '')) <= 6 THEN 'Medium' WHEN TO_NUMBER(REGEXP_REPLACE(DURATION, '[^0-9] ', '')) <= 8 THEN 'Long' ELSE 'Very Long' End As Duration_Category FROM D_SONGS