Redshift SQL 可以执行不区分大小写的正则表达式评估吗？

Question

文档说 regexp_instr() 和 ~ 区分大小写 Posix 计算函数和运算符。是否有不区分大小写的 Posix 语法，或基于 PCRE 的函数或运算符

的插件

在 Redshift 查询中尝试的 PCRE 示例，由于 POSIX'ness 而无法按预期工作。

select 
  A.target
, B.pattern
, regexp_instr(A.target, B.pattern) as rx_instr_position
, A.target ~ B.pattern as tilde_operator
, regexp_instr(A.target
, 'm/'||B.pattern||'/i') as rx_instr_position_icase
from
(      select 'AbCdEfffghi' as target 
 union select 'Chocolate' as target 
 union select 'Cocoa Latte' as target 
 union select 'coca puffs, delivered late' as target
) A
,
(      select 'choc.*late' as pattern 
 union select 'coca.*late' as pattern 
 union select 'choc\w+late' as pattern
 union select 'choc\w+late' as pattern
) B

Answer 1

回答您的问题：据我所知，没有与 Redshift 兼容的语法或插件。如果您可以使用解决方法：我们最终在字符串周围使用 lower() 来匹配：

select
  A.target
, B.pattern
, regexp_instr(A.target, B.pattern) as rx_instr_position
, A.target ~ B.pattern as tilde_operator
, regexp_instr(A.target, 'm/'||B.pattern||'/i') as rx_instr_position_icase
, regexp_instr(lower(A.target), B.pattern) as rx_instr_position_icase_by_lower
from
(      select 'AbCdEfffghi' as target
 union select 'Chocolate' as target
 union select 'Cocoa Latte' as target
 union select 'coca puffs, delivered late' as target
) A
,
(      select 'choc.*late' as pattern 
 union select 'coca.*late' as pattern 
 union select 'choc\w+late' as pattern
 union select 'choc\w+late' as pattern
) B

Answer 2

Redshift 现在通过添加的函数参数为 case-insensitive 正则表达式标志提供直接解决方案：Amazon Redshift - REGEXP_INSTR

使用提供的查询示例的语法为：

select
  A.target
, B.pattern
, regexp_instr(A.target, B.pattern) as rx_instr_position
, A.target ~ B.pattern as tilde_operator
, regexp_instr(A.target, B.pattern, 1, 1, 0, 'i') AS rx_instr_position_icase
from
(      select 'AbCdEfffghi' as target
 union select 'Chocolate' as target
 union select 'Cocoa Latte' as target
 union select 'coca puffs, delivered late' as target
) A
,
(      select 'choc.*late' as pattern 
 union select 'coca.*late' as pattern 
 union select 'choc\w+late' as pattern
 union select 'choc\w+late' as pattern
) B

Answer 3

select 'HELLO' ~* 'el' = 真

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Redshift SQL 可以执行不区分大小写的正则表达式评估吗？

Can Redshift SQL perform a case insensitive regular expression evaluation?

regex

pcre

posix

amazon-redshift