Grouped Aggregate Facts

Each group gets its own aggregate NULL facts.

highlighted = computed this step

GROUP BY forms buckets, then each bucket gets its own COUNT and SUM facts.

\text{per group facts}

Read the buckets

The compiler forms 3 groups and computes 3 aggregate facts per group.

\text{groups}=3

Aggregate NULL examples are tiny finite table transforms; SQL dialect completeness, optimizer behavior, indexing, product behavior, and performance claims are out of scope.

Each group is separate

The north group can have present-cell count zero while other groups add integers.

\text{separate buckets}

Summary

Aggregate NULL behavior is per bucket.

\text{per bucket}