Related to my previous posting
Postgresql: removing spaces between certain type of digits,
I want to do the opposite, namely to insert spaces between postal codes.
I might have a column with an address such as '01031970 São Paulo SP, BR'.
I want to insert a space between the fourth and fifth numeric digit, i.e.
'0103 1970 São Paulo SP, BR'.
Any ideas how to do it with regexp_replace?