Fetch _id of last created document of given type i

问题:

In Sanity, for a given document type named message, how can I get the _id of the newest message document?

回答1:

Query

You can actually do that in a single query in GROQ (Sanity's query language):

*[_type == 'message'] | order(_createdAt desc) [0] ._id

Query Explanation

This query has five parts.

1. *[_type == 'message']: select all documents of type 'message'.
2. |: pipe the messages (so we can perform the rest of the operations)
3. order(_createdAt desc): order the messages from newest to oldest (_createdAt is set automatically by Sanity when a document is created)
4. [0]: select the first message from the list (which is also the newest)
5. ._id: select the _id of the newest message

To fetch another property, multiple properties or the entire message object, replace the last part of the query.