postgres=# create table dabelle(inhalt text);
CREATE TABLE
postgres=# insert into dabelle values ('https://dream-nacht.xyz/images/381.jpg');
INSERT 0 1
postgres=# update dabelle set inhalt = regexp_replace(inhalt,'nacht','tag');
UPDATE 1
postgres=# select * from dabelle ;
inhalt
--------------------------------------
https://dream-tag.xyz/images/381.jpg
(1 Zeile)
postgres=#