How to find the first and last occurrences of a specific character inside a string in PostgreSQL

Question

I want to find the first and the last occurrences of a specific character inside a string. As an example, consider a string named \"2010-####-3434\", and suppose the charact

Answer 1

This pure SQL function will provide the last position of a char inside the string, counting from 1. It returns 0 if not found ... But (big disclaimer) it breaks if the character is some regex metacharacter ( .$^()[]*+ )

CREATE FUNCTION last_post(text,char) RETURNS integer AS $$ 
     select length($1)- length(regexp_replace($1, '.*' || $2,''));
$$ LANGUAGE SQL IMMUTABLE;

test=# select last_post('hi#-#-#byte','#');
 last_post
-----------
         7

test=# select last_post('hi#-#-#byte','a');
 last_post
-----------
         0

A more robust solution would involve pl/pgSQL, as rfusca's answer.