I have a CROSS JOIN query that I am using to see which combination of item quantities yield the best output.
DECLARE @last_found DECIMAL(10, 2) = 0
DECLARE @calculated DECIMAL(10, 2)
DECLARE @n_count INT
DECLARE @tbl1n INT
DECLARE @tbl2n INT
DECLARE @tbl3n INT
DROP TABLE IF EXISTS #tbl1
DROP TABLE IF EXISTS #tbl2
DROP TABLE IF EXISTS #tbl3
;WITH numbers AS (
SELECT ROW_NUMBER() OVER (ORDER BY [value]) AS n
FROM string_split('1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20', ',')
)
SELECT n, (n * 10000 * (1 + IIF(n > 1, (0.50/19.00) * (n - 1), 0))) AS price
INTO #tbl1 FROM numbers
;WITH numbers AS (
SELECT ROW_NUMBER() OVER (ORDER BY [value]) AS n
FROM string_split('1,2,3,4,5,6,7,8,9,10,11,12', ',')
)
SELECT n, (n * 15000 * (1 + IIF(n > 1, (0.50/11.00) * (n - 1), 0))) AS price
INTO #tbl2 FROM numbers
;WITH numbers AS (
SELECT ROW_NUMBER() OVER (ORDER BY [value]) AS n
FROM string_split('1,2,3,4,5,6', ',')
)
SELECT n, (n * 20000 * (1 + IIF(n > 1, (0.50/5.00) * (n - 1), 0))) AS price
INTO #tbl3 FROM numbers
SELECT
@n_count = (tbl1.n + tbl2.n + tbl3.n),
@calculated = IIF(@n_count = 10, (tbl1.price + tbl2.price + tbl3.price), 0),
@tbl1n = IIF(@calculated > @last_found, tbl1.n, @tbl1n),
@tbl2n = IIF(@calculated > @last_found, tbl2.n, @tbl2n),
@tbl3n = IIF(@calculated > @last_found, tbl3.n, @tbl3n),
@last_found = IIF(@calculated > @last_found, @calculated, @last_found)
FROM #tbl1 tbl1
CROSS JOIN #tbl2 tbl2
CROSS JOIN #tbl3 tbl3
SELECT @last_found AS highest_value, @tbl1n AS tbl1n, @tbl2n AS tbl2n, @tbl3n AS tbl3n,
t1.price AS tbl1_price, t2.price AS tbl2_price, t3.price AS tbl3_price
FROM #tbl1 t1
INNER JOIN #tbl2 t2 ON t1.n = @tbl1n AND t2.n = @tbl2n
INNER JOIN #tbl3 t3 ON t3.n = @tbl3n
As can be seen, if the query finds a value higher than the previously found highest, it is storing the combination using multiple instances of @itemN = IIF(@calculated > @last_found, tbl.n, @itemN).
Is it possible to assign all @tblXn variables in one go? I could use a CONCAT, but I think it may slow down the query, as it is a string operation.
FYI - 'n' is a value between 0 and 20.
You shouldn't be using variables for this at all.
This would be much simpler written as below (without relying on undocumented/unguaranteed behaviour of assignment to variables across multiple rows)
SELECT TOP 1 CAST(combined_price AS DECIMAL(10, 2)) AS highest_value,
tbl1.n AS tbl1n,
tbl2.n AS tbl2n,
tbl3.n AS tbl3n,
tbl1.price AS tbl1_price,
tbl2.price AS tbl2_price,
tbl3.price AS tbl3_price
FROM #tbl1 tbl1
CROSS JOIN #tbl2 tbl2
CROSS JOIN #tbl3 tbl3
CROSS APPLY (VALUES (tbl1.price + tbl2.price + tbl3.price,
tbl1.n + tbl2.n + tbl3.n)) CA(combined_price, combined_n)
WHERE combined_n = 10
ORDER BY combined_price DESC