Fuzzy Match works in two steps.
First step is Search - which is based on the Fuzzy Match key. The initial search uses Fuzzy match key, though you have not defined that in the match rule. The records from this search results would be passed to the Match rules. In the second step, the actual match happens based on the match columns you have defined, the search results would be compared/fuzzy match with the actual records.
You can define the match rule 3 as above, but there is a chance that, if the records are not filtered in the first step (because of fuzzy match key search), the records will not even participate for the match process (second step)
Fuzzy match key is used to generate ssa keys in the STRP table. And these keys are used during searching and matching to generate match candidates. If the fuzzy match key does not match, then rule 3 will not be picked up, even though the records satisfy the criteria for rule 3.
But then my confusion is that if it is a pre-requisite that the match key should match for a potential match candidate, then adding the match key to a fuzzy match rule would be redundant.
Also i think that this (match key should match) will not be applicable for an exact match rule, correct me if i'm wrong.
This rule will not be redundant. This would be used for better matching.
For Example, assume, Person_Name is the fuzzy match key.
You have a match rule with Address details. With this, you will get better results of Person_names along with Fuzzy address details.
You can define the exact rule as 'Filtered' instead of 'Exact' as well if you want to filter the exact matches based on fuzzy match key. With the 'Exact' type, fuzzy match key is not involved.
Could you please let me know -
What will be the difference if the rule is defined in below 2 ways -
a. Person_name + FZ_COL1 + EX_COL2
b. FZ_COL1 + EX_COL2
Because in either case the process will make sure that the match key is same for the two records before matching the match columns.
It depends on the Match purpose you choose.
If you are using 'Person_Name' purpose, then it might be same. But there are other match purposes available. For example, if you choose 'Address' purpose and you have included the Address Columns with that, then the results would be different here.