Count value based on the value in other table

Anonymous ,

[DNAValidation2] is a Calculated Column :

First, creating a Temp Variable to determine the Category for the particular record (i.e AP0001)

The nex VAR is creating a virtual table.  In your Table 1, I am filtering for the Category of the first VAR.

Then creating a one column table (think a cell in Excel) that concatenates all of the DNA Values for that Category.  

AP0001 only has 1 value so the result of the Concatenation is "10.10.200, 10.10.200".

Then I am searching the DNA Value in your Table 2 to see if it is contained in the concatenated value. DNA in Table 2 is "10.10.200, 10.10.200" and hence is contained in the temp value _DNA

If it is, I flag it as a 1, if not 0.

The next DNA value for AP001 (Host 14) is "10.10.200, 10.10.201".  This value is not contained within the _DNA Temp value, hence the flag =0 and Host 14 should not be counted.

Hope this explanation provides the guidance you are looking for.