"Whenever there is a one to many relationship between tables then a separate table must be loaded into the data model instead of using a mapping table and applymap."
Ive read the existing threads and tested using an example and the above statement doesnt make sense.
As long as the mapping function values are distinct the other table can have duplicate values, they will be correctly mapped. So a 1 to many relationship does work. It wont work on many to many relationship or on a one to many only if the mapping function values are the many. As long as the mapping function values are distinct the function will work correctly.
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If the table being mapped to has many 1, 1, 1, it will still work, so one to many works just depends on which table is the many, the maptable cant be the many.
The way I VIEW it one to many in mapping table doesn't make SENSE.
Anyways coming back to your question
Applymap should be used when there is one to one relationship in the mapping table or else apply map will only pick the first matching record. You can create duplicate record though by using some other functions like subfield,concat etc but that wont make much SENSE.