You can your db sum columns faster than you can grab the data, parse it, and compute the sum. In query calculations to avoid race conditions from doing the math on separate servers, etc.
Triggers and procedures are a thing.
The nosql/kv store hype missed a lot of stuff relational/sql dbs did well. Mostly because at the time they declared sql was too hard, or just never studied anything.
You can your db sum columns faster than you can grab the data, parse it, and compute the sum. In query calculations to avoid race conditions from doing the math on separate servers, etc.
Triggers and procedures are a thing.
The nosql/kv store hype missed a lot of stuff relational/sql dbs did well. Mostly because at the time they declared sql was too hard, or just never studied anything.