Permutation And Combination Between Source And Lookup Table?

how this can be achieved by writing a procedure in SQL Server DB.Remember that if there is a non-null value in the benchmark that is not equal to the equivalent criteria in the Hosting input then there is no match. Therefore those with region = IN would not match any of the given benchmarks. It is best fit as long as the non-matching values are to null value benchmark criteria.

Hosting_Site (Source File)
YEAR MONTH HOSTING CLASS REGION HOSTING COST
2015 1 A UK 75
2015 1 A IN 80
2015 1 B IN 60
2015 1 C US 100

BENCHMARK (Lookup Table)
Row Year Month Hosting class Region BENCHMARK COST
1 2015 1 A US 100
2 2015 1 B US 200
3 2015 1 A UK 50
4 2015 1 A null 70

STANDARD CLASS COST (If the criteria between source file and the lookup file doesn't match then have to load this cost)

Row Year Hosting class BENCHMARK COST
1 2015 A 22
2 2015 B 33

Then result should be:

FACT LOAD:

YEAR MONTH HOSTING CLASS REGION HOSTING COST BENCHMARK COST
2015 1 A UK 75 50
2015 1 A IN 80 70
2015 1 B IN 60 33 (Since for B class there is no region = IN or = null the Standard Class Cost must be used)
2015 1 C US 100 ??? (Reject record since there is no default value in Standard Class Cost or in Benchmark)