March 2021
Intermediate to advanced
265 pages
6h 50m
Chinese
Content preview from Presto实战
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154
｜
第
9
章
函 数 描 述
sin(
x
)
x
的正弦
asin(
x
)
x
的反正弦
tan(
x
)
x
的正切
atan(
x
)
x
的反正切
atan2(
y
,
x
)
y
/
x
的反正切
tanh(
x
)
x
的双曲正切
9.9
常数和随机函数
Presto
提供了一组函数，它们返回
数学常数
、概念值或随机值，如表
9-6
所示。
表9-6：数学常数和函数
函 数 返回类型 描 述 示 例
e() DOUBLE
欧拉数
2.718281828459045
pi() DOUBLE
圆周率
3.141592653589793
infinity() DOUBLE
用于表示无穷大的
Presto
常量
Infinity
nan() DOUBLE
用于表示不是一个数字的
Presto
常量
NaN
random() DOUBLE
大于等于
0.0
且小于
1.0
的
DOUBLE
数值
SELECT random()
random(
n
)
同输入 大于等于
0.0
并小于
n
的
DOUBLE
数值
SELECT random(100)
9.10
字符串函数和运算符
字符串操作是另一种常见的用例，对此
Presto
提供了丰富的支持。
||
操作符用于将字符串
拼接起来：
SELECT 'Emily' || ' Grace';
_col0
-------------
Emily Grace
(1 row)
Presto
提供了几个有用的字符串函数，如表
9-7
所示。
表9-7：字符串函数
函 数 返回类型 描 述 示 例
chr(
n
) VARCHAR
返回
Unicode
码点
n
代表的
单个字符
SELECT chr(65) ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.