Max function in Time

[Anonymous]

As a beginner, I would like to understand

Sum({<Year=, Month=, Quarter=, Week=, DateField=, DateNum={">=$(=Num(YearStart(Max(DateNum))))<=$(=Max(DateNum))"}>} Sales)

but not

Sum({<Year=, Month=, Quarter=, Week=, DateField=, DateNum={">=$(=Num(YearStart(DateNum)))<=$(=DateNum)"}>} Sales)

My understanding is the expression will take the value of selected Date, thus result is the same. Why is MAX function  needed here? Any implication if I use the 2nd expression?

[marcus_sommer · Accepted solution]

Referring to a field returns only a value if there is only a unique fieldvalue available - otherwise the result is NULL. Therefore the suggestion to use always aggregations, see: Use Aggregation Functions!

- Marcus

[Anonymous]

Thanks Marcus. Your answer is clear.