guarantee order of table valued function results

Question

PREMISE: The application code cannot be changed. The conditions are very specific. I am looking for something off the books, a last resort workaround if you

Answer 1

You'll have a better shot at a predictable query plan if you use a single-statement TVF instead of a multistatement TVF. ROW_NUMBER OVER should enfore the ordering you want in your RES2 query, and if it doesn't, just put it inside a CTE and order by your row number column. See below.

CREATE FUNCTION [dbo].[MyFunction]
(
/*
Parameters
*/
)
RETURNS TABLE
RETURN
WITH res2
(
    rn,
    Varchar3Col,
    DateTimeCol,
    Varchar50Col
)
AS
(
    SELECT
        ROW_NUMBER() OVER (ORDER BY action_time) AS rn,
        Varchar3Col,
        action_time AS DateTimeCol,
        Varchar50Col
    FROM
/*
        [...from statement...]
*/      
)
SELECT
    rn,
    Varchar3Col,
    DateTimeCol,
    Varchar50Col
FROM
    res2
ORDER BY
    rn;