From: | "Peter J(dot) Holzer" <hjp-pgsql(at)hjp(dot)at> |
---|---|
To: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: Regular Expression For Duplicate Words |
Date: | 2022-02-03 19:48:00 |
Message-ID: | 20220203194800.pg3bzm33dzzdpqfb@hjp.at |
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Lists: | pgsql-general |
On 2022-02-02 08:00:00 +0000, Shaozhong SHI wrote:
> regex - Regular Expression For Duplicate Words - Stack Overflow
>
> Is there any example in Postgres?
It's pretty much the same as with other regexp dialects: User word
boundaries and a word character class to match any word and then use a
backreference to match a duplicate word. All the building blocks are
described on
https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-POSIX-REGEXP
and except for [[:<:]] and [[:>:]] for the word boundaries, they are
also pretty standard.
So
[[:<:]] start of word
([[:alpha:]]+) one or more alphabetic characters in a capturing group
[[:>:]] end of word
\W+ one or more non-word characters
[[:<:]] start of word
\1 the content of the first (and only) capturing group
[[:>:]] end of word
All together:
select * from t where t ~ '[[:<:]]([[:alpha:]]+)[[:>:]]\W[[:<:]]\1[[:>:]]';
hp
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_ | Peter J. Holzer | Story must make more sense than reality.
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| | | hjp(at)hjp(dot)at | -- Charles Stross, "Creative writing
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