How to Overcome Oracle's 4000-Byte String Concatenation Limit (ORA-01489)?

ORA-01489 Error: Understanding the String Concatenation Limit

When concatenating strings in Oracle, you encounter the ORA-01489 error when the resulting string's length exceeds the SQL limit of 4000 bytes. This applies not only to standard string concatenation operators but also to functions like LISTAGG.

Workaround Using XMLAGG

To work around this limitation, you can use the XMLAGG function. XMLAGG converts the concatenated values into an XML document, effectively removing the 4000-byte restriction.

For example, instead of using LISTAGG:

LISTAGG((NUMBER || '-' || text), ',') WITHIN GROUP (ORDER BY (NUMBER || '-' || text)) AS restrictions

You can use XMLAGG:

rtrim(xmlagg(XMLELEMENT(e,text,',').EXTRACT('//text()') ).GetClobVal(),',') AS very_long_text

Other Considerations

• If you need to concatenate multiple columns that each exceed the 4000-byte limit, concatenate the XMLAGG output of each column.
• Keep in mind that XMLAGG's output is an XML fragment, so you may need to adjust your subsequent processing accordingly.

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