SELECT
    r0.sims_id,
    r0.subject,
    r1.result AS "C1",
    r2.result AS "C2",
    r3.result AS "C3"
FROM
    (SELECT DISTINCT
        sims_id, subject
     FROM
         results
     ) r0
    LEFT JOIN results r1
        ON r1.sims_id = r0.sims_id AND r1.subject = r0.subject AND r1.progress_check = 'C1'
    LEFT JOIN results r2
        ON r2.sims_id = r0.sims_id AND r2.subject = r0.subject AND r2.progress_check = 'C2'
    LEFT JOIN results r3
        ON r3.sims_id = r0.sims_id AND r3.subject = r0.subject AND r3.progress_check = 'C3'
ORDER BY
    r0.sims_id, r0.subject ;