What is the difference between the main classification number and the classification number in China patent?

China patents have a main classification number and a classification number. Among them, there is only one main classification number; There can be more than one classification number, and the classification number contains the main classification number.

Considering that the determination of the main classification number is actually arbitrary and not necessarily scientific, patents in many interdisciplinary fields are often very different. The classification number contains the main classification number. Therefore, in patent analysis, choose "classification number". If you choose the main classification number, you may lose a lot of information. But everything has advantages and disadvantages, which leads to the problem that the total statistics will exceed the number of patents.

In order to solve this problem, we will consider adjustment in the future, and at the same time give two analysis items: "main classification number" and "classification number" for selection.