What is the atom ID of double bonded carbon in TR012 molecule?
carbon refers to element = 'c'; double bond refers to bond_type = ' = ';
SELECT T1.atom_id FROM atom AS T1 INNER JOIN molecule AS T2 ON T1.molecule_id = T2.molecule_id INNER JOIN bond AS T3 ON T2.molecule_id = T3.molecule_id WHERE T2.molecule_id = 'TR012' AND T3.bond_type = '=' AND T1.element = 'c'