How get all matching positions in a string?

Question

I have a column flag_acumu in a table in PostgreSQL with values like:

\'SSNSSNNNNNNNNNNNNNNNNNNNNNNNNNNNNSNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN\'         


        

Answer 1

In Postgres 9.4 or later you can conveniently use unnest() in combination with WITH ORDINALITY:

SELECT *
FROM   dh12 d
JOIN   unnest(string_to_array(d.flag_acumu, NULL))
          WITH ORDINALITY u(elem, the_pos) ON u.elem = 'S'
WHERE  d.flag_acumu LIKE '%S%'  -- optional, see below
ORDER  BY d.codn_conce, u.the_pos;

This returns one row per match. WHERE d.flag_acumu LIKE '%S%' is optional to quickly eliminate source rows without any matches. Pays if there are more than a few such rows.

Detailed explanation and alternatives for older versions:

• PostgreSQL unnest() with element number