Sorting

The server MAY support sorting of result sets by accepting a comma‐separated list of expressions via the sort query parameter. The server SHOULD honour the client's preferences.

By default the server SHOULD sort in ascending order but MAY sort in descending order if the client prefixes an expression with a dash (-).

NULL values MUST be treated as less than non-NULL values.

Items MUST be sorted according to the order of expressions provided. The first expression defines the primary sort order; for items with identical values in the first expression, the second expression defines the secondary order, and so on.

    GET /{base}/patients?sort=-lastName
    // 200 OK
    Content-Type: application/json; charset=utf-8
    "data": {
        "patients": [
        {
            "NHSNumber": "9991234568",
            "firstName": "Bernard",
            "lastName": "Woolley",
            // ... other patient details ...
        },
        {
            "NHSNumber": "9991234567",
            "firstName": "Jim",
            "lastName": "Hacker",
            // ... other patient details ...
        },
        {
            "NHSNumber": "9991234566",
            "firstName": "Humphrey",
            "lastName": "Appleby",
            // ... other patient details ...
        }
        // ... more patients ...
        ]
    }
    }

Compound collection operations

When paging, filtering & sorting operations are performed together, the evaluation order MUST be:

1. Filtering: All filtering expressions, including range queries, MUST be applied using an AND operation.

2. Sorting: The filtered list MUST be sorted according to the specified sort criteria.

3. Paging: The sorted, filtered list MUST then be paged. This applies to both token-based and client-driven paging.