Calucate sum with specific condition

[jacek_k]

Sample data:

LOAD * INLINE [
date, index, value
1.01.2022, a, 100
1.01.2022, b, 50
2.02.2022, b, 100
];

I want to calculate sum(value) but
if index = a and index = b per exist same day sum only index = a (a have more priority, ignore b)
But if b only exist per same day sum(value) if index = b if only index a exist sum(value)

I need script flag to use it in set analysis. 

[jacek_k]

Your solution is perfect but requaire value column, what happend if I have more value column or I don`t want use value to find flag?

[jacek_k]

Hi, could you be so kind and reply to my last question?