Listagg is a great way to concatenate strings in Oracle 12. I have used it in many cases, but sometimes it is just not good enough for a very large strings. Here is the way you can use it for strings, that would not exceed 4000 chars:
SELECT FNR, ATTEST_DATO, STATUS, TYPE_FORMAAL,
LISTAGG(INNHOLD, CHR(13)||CHR(10) )
WITHIN GROUP (ORDER BY LINJENR ASC) AS INNHOLD
FROM Juridisk_Formaal
GROUP BY FNR, ATTEST_DATO, STATUS , TYPE_FORMAAL;
Here is what can be used if concatenated string would exceed 4000 chars:
SELECT FNR, ATTEST_DATO, STATUS, TYPE_FORMAAL,
XMLAGG(XMLELEMENT(e,INNHOLD,CHR(13)||CHR(10)).extract('//text()')
ORDER BY LINJENR ASC).getclobval() as INNHOLD
FROM Juridisk_Formaal e
GROUP BY FNR, ATTEST_DATO, STATUS , TYPE_FORMAAL;
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