将 CamelCase 转换为 snake_case [英] Convert CamelCase to snake_case

问题描述

需要以下查询的结果

select regexp_replace('StackOverflow', 'something', 'something')

作为

stack_overflow

推荐答案

以下正则表达式在每个大写字母前添加下划线:

The following regex adds an underscore in front of every uppercase letter:

regexp_replace(name, '([A-Z])','_\1', 'g'))

由于这会导致开头带有下划线，因此需要使用 trim()

As that results in on underscore at the beginning, this needs to be removed using trim()

trim(both '_' from lower(regexp_replace(name, '([A-Z])','_\1', 'g')))

以下查询:

with names (name) as (
  values ('StackOverflow'), 
         ('Foo'), 
         ('FooBar'), 
         ('foobar'), 
         ('StackOverflowCom')
)
select name, trim(both '_' from lower(regexp_replace(name, '([A-Z])','_\1', 'g'))) as new_name
from names;

返回:

name             | new_name          
-----------------+-------------------
StackOverflow    | stack_overflow    
Foo              | foo               
FooBar           | foo_bar           
foobar           | foobar            
StackOverflowCom | stack_overflow_com

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