How to replace every other instance of a particular character in a MySQL string?

Question

How to replace value in mysql column by query like, Column is options and its of type varchar(255)

From

id   options
1    A         


        

Answer 1

Demo

Rextester demo

Explanation

This could be solved relatively easily if only MySQL had a regular expression replacement function but unfortunately it doesn't. So I wrote one - see this blog post. The "advanced version" is needed here to allows it to perform a recursive replace in the found match for the replacement. Then the following relatively simple SQL can be used:

SQL (function code omitted for brevity)

SELECT id,
       options AS `before`,
       reg_replace(options,
                   '\\|.*\\|', -- 2 pipe symbols with any text in between
                   '\\|$',     -- Replace the second pipe symbol
                   ',',        -- Replace with a comma
                   FALSE,      -- Non-greedy matching
                   2,          -- Min match length = 2 (2 pipe symbols)
                   0,          -- No max match length
                   0,          -- Min sub-match length = 1 (1 pipe symbol)
                   0           -- Max sub-match length = 1 (1 pipe symbol)
                   ) AS `after`
FROM tbl;