Custom Association QlikSense

[tarynnagel]

I have made an association of two tables, this is a custom association of three fields from each table in QlikSense, however there is now i red line above these created fields, what does this line mean? Also, Is it better to associate or to join the tables in the data load manager?

[UserID2626]

There is no common values between two fields.

If values matching 100% it will show in green. if in orange few values matches not 100%.