How to order a query by values in different columns - coldfusion

Question

I have a recordset named rsProductClass that is returned from a table in the database. It is a very simple SELECT * FROM Table WHERE ProductID = {ID Value Here} and the table is like this:
ProductID | UPPERTIER | LOWERTIER | NATIER | OTHERTIER
1 20 60 10 10
2 10 90 NULL NULL
3 NULL 40 NULL 5
The table may or may not have a value for each of the various tiers.
What I want to do is show to the user which column has the highest value and what the name of that column is. So for example, if you were looking at ProductID 2, then the page should display "This is likely to be a LOWERTIER product"
I need to sort the rsProductClass query in such a way that it returns me a list of columns in that query ordered by the value in each column. I want to treat the NULL values as zeros.
I tried to mess about with doing valuelist() and some ArrayToList() type functions but it crashes on the NULL values. Say I add columns to an array, and then use ArraySort() to get them in some kind of order, I'll get an error saying something like "Position 1 is not numeric" because it has a NULL value.
Is this something that can be done by ColdFusion? I suppose its some sort of pivoting of the recordset which is beyond my ability.

Answer 1

Something like this would work:
<cfquery name="tiers" datasource="...">
SELECT ProductID, UPPERTIER VALUE, 'UPPERTIER' TIER
WHERE UPPERTIER IS NOT NULL
UNION
SELECT ProductID, LOWERTIER VALUE, 'LOWERTIER' TIER
WHERE LOWERTIER IS NOT NULL
UNION
SELECT ProductID, OTHERTIER VALUE, 'OTHERTIER' TIER
WHERE OTHERTIER IS NOT NULL
UNION
SELECT ProductID, NATIER VALUE, 'NATIER' TIER
WHERE NATIER IS NOT NULL
ORDER BY ProductID, VALUE
</cfquery>
<cfset productGroup = StructNew()>
<cfoutput query="tiers" group="ProductID">
<cfset productGroup[ProductID].TIER = TIER>
<cfset productGroup[ProductID].VALUE = VALUE>
</cfoutput>
<cfdump var="#productGroup#">
Starting with ColdFusion 10 you can use <cfloop query="..." group="...">, before that <cfoutput> must be used.

Answer 2

If you're willing to unpivot your query, you might do something like the following. I used COALESCE() instead of ISNULL() (either one works in this situation, but COALESCE() is the ANSI standard). The column tier_rank will give the rank of the given tier -- that is, the tier with the highest value will have a rank of 1. If there are two tiers that both have the highest value, then both will have a value in tier_rank of 1 (this is why you would use RANK() instead of ROW_NUMBER() -- you could also use DENSE_RANK() if it better fits your requirements):
SELECT p1.product_id, p1.tier_name, p1.tier_value
, RANK() OVER ( PARTITION BY p1.product_id ORDER BY p1.tier_value DESC ) tier_rank
FROM (
SELECT product_id, 'UPPERTIER' AS tier_name
, COALESCE(uppertier, 0) AS tier_value
FROM products
UNION ALL
SELECT product_id, 'LOWERTIER' AS tier_name
, COALESCE(lowertier, 0) AS tier_value
FROM products
UNION ALL
SELECT product_id, 'NATIER' AS tier_name
, COALESCE(natier, 0) AS tier_value
FROM products
UNION ALL
SELECT product_id, 'OTHERTIER' AS tier_name
, COALESCE(othertier, 0) AS tier_value
FROM products
) p1
Please see SQL Fiddle demo here.
It might be possible to re-pivot the above unpivoted query, but I must admit my attempts at doing so failed.

Answer 3

I had to do something similar to this recently and looked into UNPIVOT in SQL Server. Going with the suggestion to Unpivot your query like David said, you could do something like this. This doesn't add RANK column, but it does order the values.
SELECT ProductID, Tier, TierValue
FROM
(SELECT ProductID, ISNULL(UpperTier,0) UpperTier, ISNULL(LowerTier,0) LowerTier, ISNULL(NaTier,0) NaTier, ISNULL(OtherTier,0) OtherTier
FROM products) p
UNPIVOT
(TierValue FOR Tier IN
(UpperTier, LowerTier, NaTier, OtherTier)
)AS unpvt
ORDER BY ProductID, TierValue Desc
SQL FIDDLE