Hello. We currently have a private preview for Partial record updates (aka Patch) available for sign-up.
If you are interested in signing up for this private preview program, please visit, https://aka.ms/cosmosdbpatch
There are multiple responses to this suggestion.
Support for SQL-like syntax for UPDATE, DELETE and INSERT INTO are not on our road map at this time.
However, the underlying functionality for an UPDATE, SET is essentially a PATCH. This functionality we are actively working on. See this User Voice item here to track for future updates. https://feedback.azure.com/forums/263030-azure-cosmos-db/suggestions/6693091-be-able-to-do-partial-updates-on-document
Thank you for your suggestion.