Oracle Regular expression
Let's say we want to replace only numbers with 2 digits: regular expression will find them with (\d\d)
If I want to swap parts of the text, I use \1, \2, \3 to call for the matched strings:
SUBSTR retrieves part of a string by indicating the starting position and the number of characters to extract
To count from the end of the string, SUBSTR accepts a negative number as the second parameter, e.g.
To get the last character in a string: SUBSTR(mystring,-1,1)