Data engineering·Modelling for analysis
someone asked what one row means and three people in the room gave three different answers.
Grain
Also calledgranularity, level of detail
The precise meaning of a single row in a table, stated as a sentence: one row per order line per day, one row per session. Declaring it before anything else is the single most load-bearing habit in modelling, because every join, every sum and every duplicate bug is a grain question in disguise. A table whose grain nobody can state will, given time, be joined at the wrong level and quietly double a number.