How many molecules have a double bond type and among these molecule, how many are labeled as carcinogenic compound?
double bond refers to bond_type = ' = '; label = '+' mean molecules are carcinogenic;
SELECT COUNT(DISTINCT T2.molecule_id), SUM(CASE WHEN T2.label = '+' THEN 1 ELSE 0 END) FROM bond AS T1 INNER JOIN molecule AS T2 ON T1.molecule_id = T2.molecule_id WHERE T1.bond_type = '='