Question

I have a data table as follows

FName  SName  DOB  PCode   Addr1     
====   ==== ====== =====   =======  
Bob    Test 231280 S66TH   1 Test Lane  
Bobby  Test 240977 S66TH   2 Test Drive
Robert Test 240977 xxxxx   xxxxxx
Tim    Test 140977 S78YH   5 Hill Road

I am trying to write a function / SP that will accept Paramters FNAme, SName, Dob, PCode and Addr1. I want to be able to match records where ANY 3 out of the 5 parameters are equal. I’m not sure how to do this WITHOUT writing a long series of AND OR statements? I would quite like the solution to be scalable too so if in future another column is added then 3 out of 6 must match (or even 4 out of 6). I dont mind the query being represented by Linq either.

Essentially Im looking for a matching algorithm That can match x out of y pieces of data.

Answer 1

Convert true comparisons to 1, false comparisons to 0, add them all together, and test if the sum is at least 3. Something like

where (case FName when @FName then 1 else 0 end)
    + (case SName when @Sname then 1 else 0 end)
    + (case DOB   when @DOB   then 1 else 0 end)
    + (case PCode when @PCode then 1 else 0 end)
    + (case Addr1 when @Addr1 then 1 else 0 end)
    >= 3