Hello @Terence_Leung,
You can almost always do this, in any system but it often requires two calls :slightly_smiling_face:
1) Search for records based on your own filter criteria (“unique_id” == “1234567”)
If it is really a “unique” field, then it should only return one result. Just get the first item of the returned array and get it’s record ID.
2) Update your base record using record ID found in step (1)
I don’t think it’s possible to do it in one step using the API, as mentioned in their documentation :
[…] objects should have an id property representing the record ID […]
Florian VERDONCK