can not find patent ID in CPC Current file
Hi,
I would like to examine the patent's classification, so I try to merge the patent file with the "CPC current" file using the key of "patent id". However, I find many "patent id" in the patent file is not exist in the "CPC current" file. For example, the patent id of "10082717", " D255049", "PP12973" can not be found in the "CPC current" file. Does this mean that the "CPC current" file misses many patent id and the "CPC current" file is not complete? If I would like to find all the patent's classification, what file should I use?
Thank you very much for your help!
Best,
Yijia