Hi @Kai_Zhu welcome to the Coda community!
Upsert is an amalgam of
Update. Its best used when you are uncertain if the row exists.
If you try to
Update a row that doesn’t exist, the zap will fail. If you try to
Insert a row that already exists, the zap will fail.
Upsert will always work … but sometimes you do want it to fail. It gives you more flexibility depending on the use case.
Alright, so this is just a non-English speaker’s misunderstanding.