update tablename set zipcode = concat(substr(zipcode,1,3) , ' ', substr(zipcode,4,3) ) where 0=0 and zipcode regexp '^[A-Z][[:digit:]]' and substr(zipcode,4,1) <> ' ' and length(zipcode) = 6
update tablename set zipcode = concat(substr(zipcode,1,3) , ' ', substr(
zipcode
,4,3) ) where 0=0 and zipcode regexp '^[A-Z][[:digit:]]' and substr(zipcode,4,1) <> ' ' and length(zipcode) = 6