Duplicate entry error for unique key that doesn't exist
Your update is the correct way to insert data. Using
INSERT INTO ... SELECT ... requires a source table and is not meant to be used with static values.

Using INSERT INTO ... VALUES ... is for inserting static data, such as CCC, into the table. The two are not interchangable and will cause the issues you've been seeing.

You can check the documentation on INSERT INTO ... SELECT ... here and note that it only talks about using a table source.