sum
sum 介绍
sum(expr) - 返回根据一个组中的值计算出的总和。
Examples:
> SELECT sum(col) FROM VALUES (5), (10), (15) AS tab(col);
30
> SELECT sum(col) FROM VALUES (NULL), (10), (15) AS tab(col);
25
> SELECT sum(col) FROM VALUES (NULL), (NULL) AS tab(col);
NULLSince: 1.0.0