Distribute values over value-range tiers - sql-server

Question

I have two tables: a list of Total Sales Per Employee, and a list of Compensation Tiers
Employee Sales | Comp Tiers
============== | ===================
EmpID Sales | TierID MaxAmt Rate
1 12000 | 1 10000 20% -- Up to $10k sales compensated at 20%
2 17000 | 2 15000 25% --The next $5k sales compensated at 25%
3 23000 | 3 20000 30% --The next $5k sales compensated at 30%
4 31000 | 4 25000 40% --The next $5k sales compensated at 40%
| 5 99999 50% --Any remaining sales compensated at 50%
Based on these inputs, I need to split each employee's Sales over each Tier based on each tier's MaxAmt value to calculate compensation rates at each tier. Further, I don't want to hard-code calculations for each tier as the number of tiers may change over time. (On second thought, I don't mind hard-coding, as long as it can handle UP-TO 5 tiers. Sounds fair?)
Desired Output:
EmpID Sales TierID TierAmt Rate Net
=========================================
1 12000 1 10000 20% 2000
1 12000 2 2000 25% 500
2 17000 1 10000 20% 2000
2 17000 2 5000 25% 1250
2 17000 3 2000 30% 600
3 23000 1 10000 20% 2000
3 23000 2 5000 25% 1250
3 23000 3 5000 30% 1500
3 23000 4 3000 40% 1200
4 31000 1 10000 20% 2000
4 31000 2 5000 25% 1250
4 31000 3 5000 30% 1500
4 31000 4 5000 40% 2000
4 31000 5 6000 50% 3000
I'm not unskilled with SQL, but I can't even fathom an appropriate strategy. Any ideas? Changes to table structure are permissible if it helps achieve the goal.
SQLFiddle

Answer 1

Lets make some test data:
DECLARE #EmpSales TABLE
(
EmpID INT,
Sales INT
)
INSERT INTO #EmpSales
VALUES
( 1, 12000 ),
( 2, 17000 ),
( 3, 23000 ),
( 4, 31000 );
DECLARE #CompTiers TABLE
(
TierID INT,
MaxAmount INT,
Rate DECIMAL(10,2)
)
INSERT INTO #CompTiers
VALUES
( 1, 10000, .20 ),
( 2, 15000, .25 ),
( 3, 20000, .30 ),
( 4, 25000, .40 ),
( 5, 99999, .50 );
Here I make a CTE to find all of the tiers and the previous (to get the top and bottom of the tier)
WITH Tiers AS
(
SELECT
n.TierID,
n.MaxAmount,
n.Rate,
ISNULL(p.MaxAmount, 0) PrevAmount
FROM #CompTiers n
LEFT JOIN #CompTiers p
ON p.TierID = n.TierID - 1
),
Lets take the tier CTE and cross join it against the sales picking only the tiers where the sales is greater than the prevamount (bottom of the tier).
SalesComp AS
(
SELECT *
FROM #EmpSales e
CROSS JOIN Tiers c
WHERE Sales > PrevAmount
)
Now that we have the data matched up, just clean it up with some cases:
SELECT
s.EmpID,
s.Sales,
s.TierID,
CASE
WHEN s.Sales > s.MaxAmount THEN s.MaxAmount - s.PrevAmount
ELSE s.Sales - s.PrevAmount
END TierAmount,
s.Rate,
CASE
WHEN s.Sales > s.MaxAmount THEN (s.MaxAmount - s.PrevAmount) * s.Rate
ELSE (s.Sales - s.PrevAmount) * s.Rate
END Net
FROM SalesComp s
ORDER BY EmpID, TierID
Here is the output:
EmpID Sales TierID TierAmount Rate Net
1 12000 1 10000 0.20 2000.00
1 12000 2 2000 0.25 500.00
2 17000 1 10000 0.20 2000.00
2 17000 2 5000 0.25 1250.00
2 17000 3 2000 0.30 600.00
3 23000 1 10000 0.20 2000.00
3 23000 2 5000 0.25 1250.00
3 23000 3 5000 0.30 1500.00
3 23000 4 3000 0.40 1200.00
4 31000 1 10000 0.20 2000.00
4 31000 2 5000 0.25 1250.00
4 31000 3 5000 0.30 1500.00
4 31000 4 5000 0.40 2000.00
4 31000 5 6000 0.50 3000.00

Answer 2

The idea behind the following query happens to be same as the one in Kevin Cook's answer and the two solutions differ mainly by syntax:
WITH TierRanges AS (
SELECT
*,
MinAmt = LAG(MaxAmt, 1, 0) OVER (ORDER BY MaxAmt)
FROM
CompTiers
)
SELECT
s.EmpID,
s.Sales,
t.TierID,
x.TierAmt,
t.Rate,
Net = x.TierAmt * t.Rate
FROM
EmpSales AS s
INNER JOIN
TierRanges AS t ON s.Sales > t.MinAmt
CROSS APPLY
(
SELECT CASE WHEN s.Sales > t.MaxAmt THEN t.MaxAmt ELSE s.Sales END - t.MinAmt
) AS x (TierAmt)
ORDER BY
s.EmpID,
t.TierID
;
The TierRanges CTE "enhances" the CompTiers row set with a MinAmt column to form a tier range together with MaxAmt, MinAmt being the previous tier's MaxAmt value (or 0, for the first tier). This can be considered a direct equivalent of the other answer's Tiers CTE, but you can see that here the LAG function is used instead of a self-join, and the former is likely to work faster than the latter.
The main query joins every row in EmpSales with every row in TierRanges where EmpSales.Sales exceeds TierRanges.MinAmt. (In the other answer this part is implemented separately from the main query as another CTE, SalesComp.) To get the tier amount, it subtracts the MinAmt value from either Sales or MaxAmt, depending on which one is lesser. Because the tier amount is needed twice in the query (once for the output as is and the second time to get Net), CROSS APPLY is used to avoid repetition of code.
Because of LAG, SQL Server 2012 is the minimum version required to run the query.

Answer 3

try using a full outer (cross) join between the tables as long as the sales amount is less than or equal to the tier max amount

Answer 4

With Beth's suggestion as a jumping-off point, I worked my way through the rest to come up with a workable solution. It starts with a CROSS JOIN to show all possible combinations of Sales and Tiers, filters out those with Sales out of range of their matched Tier, and uses a Recursive CTE to work through each Tier's calculation using the prior Tier results.
;WITH
/* CROSS JOIN Sales and Tiers, and then ***/
/** filter to only relevant Tiers for each Emp. **/
/*** Also include Prior Tier [MaxAmt] value. */
combos AS
( SELECT s.EmpID,s.Sales,t.TierID,
[MaxAmt-1] = t0.MaxAmt,
[MaxAmt] = t.MaxAmt
FROM EmpSales s
CROSS JOIN CompTiers t
LEFT JOIN CompTiers t0 ON t0.TierID = t.TierID-1 --Prior Tier
WHERE s.Sales > ISNULL(t0.MaxAmt,0) --Filter out irrelevant Tiers given Sales
),
cte AS
/* Calculate Tier1 Sales, then use Recursive CTE **/
/** to calculate other Tiers based on prior Tier values */
( SELECT c.*,
TierAmt = CAST(CASE
WHEN c.Sales > c.[MaxAmt]
THEN c.[MaxAmt]
ELSE c.Sales END AS MONEY)
FROM combos c
WHERE c.TierID = 1
UNION ALL
SELECT c.*,
TierAmt = CAST(CASE
WHEN c.Sales > c.[MaxAmt]
THEN c.[MaxAmt]-ISNULL(c.[MaxAmt-1],0.0)
ELSE c.Sales-ISNULL(c.[MaxAmt-1],0) END AS MONEY)
FROM cte
JOIN combos c ON c.EmpID = cte.EmpID
WHERE c.TierID = cte.TierID+1
)
/* Combine [TierAmt] and [Rate] at each Tier */
/** to calculate Net Pay amount. **/
SELECT cte.EmpID,cte.Sales,cte.TierID,cte.TierAmt,
t.Rate,
Net = t.Rate * cte.TierAmt
FROM cte
LEFT JOIN CompTiers t ON t.TierID = cte.TierID
ORDER BY EmpID,TierID
I invite feedback, enhancements, and alternatives.
SQLFiddle