fieldname=regexp_replace(fieldname,old_sub_string,new_sub_string)
Add a 'g' flag:
fieldname=regexp_replace(fieldname,old_sub_string,new_sub_string, 'g')
From the end of a paragraph in 9.7.3 just before 9.7.3.1:
The flags parameter is an optional text string containing zero or more single-letter flags that change the
function’s behavior. Flag i specifies case-insensitive matching, while flag g specifies replacement of each
matching substring rather than only the first one.
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