title: posix regexp to split a table
body: <p>I'm currently working on data migration in PostgreSQL. Since I'm new to posix regular expressions, I'm having some trouble with a simple pattern and would appreciate your help.</p>
  
  <p>I want to have a regular expression split my table on each alphanumeric char in a column, eg. when a column contains a string <code>'abc'</code> I'd like to split it into 3 rows: <code>['a', 'b', 'c']</code>. I need a regexp for that</p>
  
  <p>The second case is a little more complicated, I'd like to split an expression <code>'105AB'</code> into <code>['105A', '105B']</code>, I'd like to copy the numbers at the beginning of the string and split the table on uppercase letters, in the end joining the number with exactly 1 uppercase letter.</p>
  
  <p>the function I'll be using is probably <code>regexp_split_to_table(string, regexp)</code></p>
  
  <p>I'm intentionally providing very little data not to confuse anyone, since what I posted is the essence of the problem. If you need more information please comment.</p>