Civil law can have a jury as well. The difference is that common law is based on reasonableness and precedents, while civil law is a matter of statute.
(US) Apples and oranges, or more appropriately, caterpillars and butterflies. The criminal and civil laws arise from the common law. Some of them are more codified but the foundation is common law.
Common law is ‘case law” in that is isn’t written in a code book but instead in case books.
Under civil law, the jury is charged only with deciding the facts of a case and not the law itself. A common law jury has much more power and flexibility. Unfortunately, most accused don't know how to invoke common law rights and end up in either an equity or admiralty court proceeding, in which case they are guilty until proven innocent.