How can I write a query to extract individual changes from snapshots of data?

Question

I need to create a process that will extract the changes from a table where each row is a snapshot of a row in another table. The real-world problem involves many tables wit

Answer 1

WITH Snapshots (Sequence, DateTaken, ID, Field, FieldValue, _Index) AS
(
    SELECT
        Sequence,
        DateTaken,
        ID,
        'Field1' AS Field
        CAST(Field1 AS VARCHAR(100)) AS FieldValue,  -- Find an appropriate length
        ROW_NUMBER() OVER (ORDER BY ID, Sequence)
    FROM
        #Snapshots
    UNION ALL
    SELECT
        Sequence,
        DateTaken,
        ID,
        'Field2' AS Field
        CAST(Field2 AS VARCHAR(100)) AS FieldValue,  -- Find an appropriate length
        ROW_NUMBER() OVER (ORDER BY ID, Sequence)
    FROM
        #Snapshots
)
SELECT
    S1.DateTaken,
    S1.ID,
    S1.Field,
    S1.FieldValue AS Previous,
    S2.FieldValue As New   -- Not necessarily "Current"
FROM
    Snapshots S1
INNER JOIN Snapshots S2 ON
    S2.ID = S1.ID AND
    S2.Field = S1.Field AND
    S2._Index = S1._Index + 1 AND
    S2.FieldValue <> S1.FieldValue    -- Might need to handle NULL values