正確寫法：先處理null值邏輯。

= Table.AddColumn(重命名的列, "IsTOGreaterThan0", each if [TurnoverCurrentYear] = null then "Y" else if [TurnoverCurrentYear] >0 then "Y" else "N")

錯誤寫法：
= Table.AddColumn(重命名的列, "IsTOGreaterThan0", each if [TurnoverCurrentYear] >0 then "Y" else if [TurnoverCurrentYear] is null then "Y" else "N")

Ref：Power Query里多條件判斷時需要注意的null值處理問題_51CTO博客_power query null