July 2023
Intermediate to advanced
278 pages
5h 40m
Chinese
Content preview from Trino 权威指南：原书第2版
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174
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第
9
章
函数 返回类型 描述 示例
trim(
string
) VARCHAR 从后往前计算
，
删除头部
和尾部空格
。
与同时使用
rtrim
和
ltrim
效果一样
SELECT trim(
'
A
'
)
upper(
string
) VARCHAR 将字符串转换为大写 SELECT upper('lower')
word_stem(
word,
lang
)
VARCHAR 返回指定语言下单词的词干 SELECT word_stem
('trino', 'it')
9.11
字符串和映射
Trino
能够处理映射类型的数据，它有两个可以返回映射类型的字符串函数：
split_to_map(string, entryDelimiter, keyValueDelimiter) → map<varchar, varchar>
该函数通过使用
entryDelimiter
将
string
参数分割，将字符串拆成包含键值对的字符
串，然后使用
keyValueDelimiter
将这些字符串拆成键和值，其结果是一个映射。
下面是该函数的一个实例
—
解析
URL
参数：
SELECT split_to_map('userid=1234&reftype=email&device=mobile', '&', '=');
_col0
---------------------------------------------
{device=mobile, userid=1234, reftype=email}
(1 row)
当同一个键出现多次时，
split_to_map ...
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