Data engineering·Quality, tests and knowing it is wrong
the column has been two percent null for a year, this morning it is sixty percent, and nothing else changed.
Null-rate check
Also callednull check, completeness check
Monitoring the proportion of missing values in a column against its normal range rather than against zero. It catches upstream breakages with unusual precision, because a failed join or a renamed source field usually shows up first as a column that has gone empty. Testing for 'not null' misses this entirely, since the real signal is the change in the rate rather than the presence of any nulls at all.