There is a difference. Witnesses are mainly engaged in operations and can understand trade terms and document preparation. According to the work, the merchandiser is about how to get a ticket, and is responsible for the connection of all aspects in the process of getting the goods.

As for customs declarers and customs declarers, customs declarers deal with the commodity inspection bureau. If your company's products need to be inspected, you need to apply for a certificate at the Commodity Inspection Bureau. You can know which countries have requirements for export products and which goods need to be inspected. Usually now it's double certificates, that is, inspection and customs declaration.

Customs declaration deals with customs. Some companies declare themselves, and some declare through freight forwarders. Personally, I feel that the gold content of the customs broker's card is higher, because it is the same as the inspection. In fact, if you want to do trade, I think it is necessary to know about these four. But it depends on your future career. The so-called profession has specialization. Besides the textual research you mentioned, I think you should be familiar with the literature and documents, but it doesn't matter whether you take the exam or not.