聚合函数

avg

求平均

avg(number T) -> T

SELECT avg(age) LIMIT 1

sum

求和

sum(number T) -> T

SELECT sum(age) LIMIT 1

min

最小值

min(number T) -> T

SELECT min(age) LIMIT 1

max

最大值

max(number T) -> T

SELECT max(age) LIMIT 1

count

次数

count(field) -> integer ,

count(*) -> integer ,

count(1) -> integer

SELECT count(age) LIMIT 1 ,

SELECT count(*) LIMIT 1 ,

SELECT count(1) LIMIT 1