conditional join in ds

[bhargav_dd]

I have a requirement where in i need to join 2 tables based on 2 keys.
But the keys will change according to value of one column in reference
table.
Scenario is:
Table A is primary table and Table B is reference table. and the keys are
key1 and key2. Now I need to join these tables on both the keys if value of
column1 in reference table is let's say "XYZ". if the value of the column1
is "ABC" then I need to join based on only one key i.e. key1.
The join in both the cases will be an Inner Join
Any idea how to achieve this in DS?