df5=pd.read_sql('''SELECT *,to_char(year,'9999')years FROM CO_DEUX WHERE code LIKE 'USA' AND year BETWEEN 1980 AND 2017 OR code LIKE 'CHN' AND year BETWEEN 1980 AND 2017;''',con=co)
df6=pd.read_sql('''SELECT *,to_char(year,'9999')years FROM CO_DEUX WHERE code LIKE 'USA' AND year BETWEEN 1980 AND 2017 OR code LIKE 'CHN' AND year BETWEEN 1980 AND 2017;''',con=co)