NTILE with uneven bucket sizes

Question

Accepted Answer

With 5 rows and NTILE(2), the buckets cannot be perfectly equal. SQL distributes the extra row to the earlier buckets: bucket 1 gets 3 rows (Alice, Bob, Carol), bucket 2 gets 2 rows (Dave, Eve). Dave is in bucket 2. The rule is that earlier buckets receive the extra rows when division is uneven - bucket 1 always gets ceil(n/k) rows. This can surprise you when you expect exactly equal splits; NTILE guarantees the sizes differ by at most 1.