Get substring from regular expression - everything up to a character - regex

Question

There is a questions table with a column called options which contains
'r>>>>>5####answer1|4####answer2|3####answer3|2####answer4|1####answer5'
Which are pairs of possible answers
5 = answer1
4 = answer2
etc.
The questions are set up by users but the pattern is the same.
Another table has a users answer which is the option selected. I'm attempting to write SQL to extract the answer text.
For example 4 should display answer2.
I tried:
SELECT substring(question.options from '%4#####"%#"[\|]%' for '#') AS answertext
FROM ...
But it displays answer2|3####answer3|2####answer4.
How do I get everything up to the first |?

Answer 1

The regular expression supplied by #Abelisto in a comment works nicely. You don't need to escape | in the character class, so it can be:
SELECT substring(options, '4#+([^|]+)' ...
Assuming the number of the answer is limited to a single digit, there is a simple solution without regular expressions, too:
SELECT right(x, -5) AS answer
FROM unnest( string_to_array(right(
'r>>>>>5####answer1|4####answer2|3####answer3|2####answer4|1####answer5'
, -6), '|')) x
WHERE x LIKE '4%'; -- pick number
Applied to your table:
SELECT right(x, -5) AS answer
FROM question q, unnest( string_to_array(right(q.options, -6), '|')) x
WHERE q.question_id = 1
AND x LIKE '4%';
But really, you should normalize your unfortunate design. It's a 1:n design between question and answers. Assuming a PK question.question_id you can fix it quickly like this:
CREATE TABLE answer AS
SELECT q.question_id, left(x,1)::int AS answer_id, right(x, -5) AS answer
FROM question q, unnest(string_to_array(right(q.options, -6), '|')) x;
ALTER TABLE answer
ADD PRIMARY KEY (question_id, answer_id)
, ADD CONSTRAINT q_fk FOREIGN KEY (question_id) REFERENCES question(question_id)
ON UPDATE CASCADE ON DELETE CASCADE;
ALTER TABLE question DROP column options;
Then your query simply is:
SELECT answer
FROM answer
WHERE question_id = 1
AND answer_id = 4;
Related:
How to implement a many-to-many relationship in PostgreSQL?