Hi, Peter, Interesting. On Thu, 3 Feb 2022 at 19:48, Peter J. Holzer <hjp-pg...@hjp.at> wrote:
> 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[[:>:]]'; > > Give a good example if you can. > Regards, David
