Cosmos DB - Deleting a document

The DocumentDB API's SQL is specifically for querying. That is, it only provides SELECT, not UPDATE or DELETE.

Those operations are fully supported, but require REST (or SDK) calls. For example, with .net, you'd call DeleteDocumentAsync() or ReplaceDocumentAsync(), and in node.js, this would be a call to deleteDocument() or replaceDocument().

In your particular scenario, you could run your SELECT to identify documents for deletion, then make "delete" calls, one per document (or, for efficiency and transactionality, pass an array of documents to delete, into a stored procedure).

The easiest way is probably by using Azure Storage Explorer. After connecting you can drill down to a container of choice, select a document and then delete it. You can find additional tools for Cosmos DB on https://gotcosmos.com/tools.