SQL语句实现两张表之间同步数据，不存在则插入

INSERT into contract_service.voucher_contract_mapping_info (uuid,contract_id, contract_name,external_contract_id,external_contract_name)
select uuid,code,name,'','' from contract_service.contract_info a
EXCEPT
select a.uuid,code,name,'','' from contract_service.contract_info a join contract_service.voucher_contract_mapping_info  b
on a.code=b.contract_id
go