Module 4 · DAX for harder questions Lesson 11 of 15
Distinct counts and semi-additive measures
Some numbers must not be added across time: a headcount of 100 in January plus 100 in February is not 200 people. Distinct counts and the latest-value pattern keep those numbers honest.
Worked example
DISTINCTCOUNT(fact_sessions[user_id]) counts unique users; averaging it across days is wrong unless the report says "average daily users".
Your practice task
Create a distinct-count measure for users and a month-end measure for headcount, and explain in the tooltip why they are not summed.
Do this before moving on. Reading a solution teaches the shape of it; typing it teaches you.
Key takeaway
Some numbers must not be added across time: a headcount of 100 in January plus 100 in February is not 200 people. Distinct counts and the latest-value pattern keep those numbers honest.
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