Total

sum x    sum[x]

Where x is

• a simple numeric list, returns the sums of its items
• an atom, returns x
• a list of numeric lists, returns their sums
• a dictionary with numeric values

Nulls are treated as zeros.

q)sum 7                         / sum atom (returned unchanged)
7
q)sum 2 3 5 7                   / sum list
17
q)sum 2 3 0N 7                  / 0N is treated as 0
12
q)sum (1 2 3 4;2 3 5 7)         / sum list of lists
3 5 8 11                        / same as 1 2 3 4 + 2 3 5 7
q)sum `a`b`c!1 2 3
6
q)\l sp.q
q)select sum qty by s from sp   / use in select statement
s | qty
--| ----
s1| 1600
s2| 700
s3| 200
s4| 600
q)sum "abc"                     / type error if list is not numeric
'type
q)sum (0n 8;8 0n) / n.b. sum list of vectors does not ignore nulls
0n 0n
q)sum 0n 8 / the vector case was modified to match sql92 (ignore nulls)
8f
q)sum each flip(0n 8;8 0n) /do this to fall back to vector case
8 8f

sum is an aggregate function, equivalent to +/.

❯ q -s 4
KDB+ 4.0 2021.01.20 Copyright (C) 1993-2021 Kx Systems
m64/ 12()core 65536MB sjt mackenzie.local 127.0.0.1 ..

q)\s 0
q)a:100000000?1.
q)\P 0
q)sum a
49999897.181930684
q)sum reverse a
49999897.181931004

q)\s 4
q)sum a
49999897.181933172