• SELECT p.*, x.*

    FROM Projects p

    CROSS APPLY (

    SELECT TOP 1 *

    FROM ProjectCategory pc

    WHERE pc.ProjectID = p.ProjectID

    ORDER BY NEWID()

    ) x

    “Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

    For fast, accurate and documented assistance in answering your questions, please read this article.
    Understanding and using APPLY, (I) and (II) Paul White
    Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden