sum(A) + sum(B) = sum(A ∪ B) sum(A) + sum({}) = sum(A ∪ {}) sum(A) + sum({}) = s... | Hacker News

Hacker News new | past | comments | ask | show | jobs | submit

login

eurleif on July 22, 2013 | parent | context | favorite | on: Things in SQL Server which don't work as expected

    sum(A) + sum(B) = sum(A ∪ B)
    sum(A) + sum({}) = sum(A ∪ {})
    sum(A) + sum({}) = sum(A)
    sum({}) = 0

dbaupp on July 22, 2013 [–]

(This assumes either A and B are multisets, or they are disjoint.)

kragen on July 22, 2013 | [–]

Indeed, but in the context of minor changes in how things SQL should behave, we can assume that everything is a multiset.

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact