How to split comma separated string inside stored procedure?

Question

How to split comma separated string into strings inside store procedure and insert them into a table field?

Using Firebird 2.5

Answer 1

This works for me on an Informix DataBase:

DROP FUNCTION rrhh:fnc_StringList_To_Table;
CREATE FUNCTION rrhh:fnc_StringList_To_Table (pStringList varchar(250))
    RETURNING INT as NUMERO;

    /* A esta Funcion le podes pasar una cadena CSV con una lista de numeros
     *      Ejem:  EXECUTE FUNCTION fnc_StringList_To_Table('1,2,3,4');
     * y te devolvera una Tabla con dichos numeros separados uno x fila
     * Autor:  Jhollman Chacon @Cutcsa - 2019 */

    DEFINE _STRING VARCHAR(255);
    DEFINE _LEN INT;
    DEFINE _POS INT;
    DEFINE _START INT;
    DEFINE _CHAR VARCHAR(1);
    DEFINE _VAL INT;

    LET _STRING = REPLACE(pStringList, ' ', '');
    LET _START = 0;
    LET _POS = 0;
    LET _LEN = LENGTH(_STRING);

    FOR _POS = _START TO _LEN
        LET _CHAR = SUBSTRING(pStringList FROM _POS FOR 1);

        IF _CHAR <> ',' THEN 
            LET _VAL = _CHAR::INT;
        ELSE 
            LET _VAL = NULL;
        END IF;

        IF _VAL IS NOT NULL THEN 
            RETURN _VAL WITH RESUME;
        END IF;

    END FOR;

END FUNCTION;

EXECUTE FUNCTION fnc_StringList_To_Table('1,2,3,4');
SELECT * FROM TABLE (fnc_StringList_To_Table('1,2,3,4'));