Question

I have two tables:

PARENT (EMAIL,NAME,ETC)
CHILD (EMAIL,DOC_DOC_ID,DOWNLOAD_DATE,RANK)

I need to generate a query that will update the CHILD.RANK Field, with a numerical sorting that will rank each distinct DOC_ID by the date that it was downloaded (1 = latest doc download)

SELECT
    P.EMAIL,
    C.DOC_ID,
    MAX(C.DOWNLOAD_DATE)
FROM
    PARENT P,
    CHILD C
WHERE
    P.EMAIL = C.EMAIL

Please dont laugh at what i have come up with so far!… i think my brain is fried!

Answer 1

If you are using Rank_ID for more than display (which should be left to the queries) your design may have issues.

Have you considered what would happen if you checked out DOC_ID = 1 today and then ran an update to give it rank one and then the same thing happened tomorrow and you now have two records for DOC_ID = 1 with a RANK of 1?

You could use something like this to just display the records in the correct order. Query 1 will just display the records in order. Query 2 will add a Rank value (requires the first query).

QUERY 1:
SELECT
    LAST(EMAIL) AS EMAIL,
    DOC_DOC_ID,
    Max(DOWNLOAD_DATE) AS DOWNLOAD_DATE
FROM 
    CHILD
GROUP BY 
    DOC_DOC_ID
ORDER BY 
    Max(DOWNLOAD_DATE) DESC;


QUERY 2:
SELECT 
    testing.EMAIL, 
    testing.DOC_DOC_ID, 
    testing.DOWNLOAD_DATE, 
    (select 
         count(*)
     from
         Query1
     where
         DOWNLOAD_DATE>testing.DOWNLOAD_DATE)+1 AS RANK
FROM
    Query1 as testing
ORDER BY
    testing.DOWNLOAD_DATE DESC;