How to update document by adding key-value in Couchbase

SQL++
2

Simply set the new key-value.

UPDATE bucket SET key3 = "value3" WHERE "key1" = "value1";

UPDATE works in sets like SQL. If you know the document to update, use the USE KEYS clause otherwise, use the WHERE clause carefully.

UPDATE bucket USE KEYS "mykey" SET key3 = "value3" ;