Thank you for your advice. Christian Do you mean to calculate the column under the "Derived from physical mappings" instead of the "Derived from existing columns using an expression"? I tried to calculate under the Table Job History for the start date and end date. it works.

Thanks for your reply. Gianni I guess I have to work under the rules then. I could calculate a different logical column as an attribute instead, which is great to know!

Thank you for your patience and advice. Gianni Yes my 4LTS are snowflake in physical diagram. I didn't know that I could put them in one LTS even though they don't have a parent child table. You are very helpful! Thanks again!