PostgreSQL中的Oracle EXTRACT xml

Question

I'm right in the middle of migration from Oracle to PostgreSQL and I have problem with something like that:

RTRIM(XMLAGG(XMLELEMENT(e,'WZ-'||C.docnum,'; ')
.EXTRACT('//text()') ORDER BY C.docnum).GetClobVal(),'; ') As x

How to convert it on PostgreSQL? Thanks in advance

Answer 1

As far as I can tell this is using XMLAGG only because Oracle's listag() can't handle strings larger than 4K (or 32K in Oracle 12).

So I think what you want is a simple:

string_agg('WZ-'||c.docnum, '; ' order by c.docnum)

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If docnum can be NULL you maybe want:

string_agg(concat('WZ-', c.docnum), '; ' order by c.docnum)

because concat() will treat null values as an empty string ( || will yield null if any of the values involved is null )