How to Overcome Oracle's 'Result of String Concatenation is Too Long' Error When Using LISTAGG?

Solving the "String concatenation result is too long" error in Oracle's LISTAGG function

An alternative is needed when the LISTAGG function encounters a large amount of data and throws a "String concatenation result is too long" error.

Solution of XMLAGG function

In order to achieve similar functionality to LISTAGG, Oracle's XMLAGG function can be used. The XMLAGG function aggregates data into an XML document, allowing concatenated values ​​to exceed the LISTAGG limit. The following syntax demonstrates how to use XMLAGG:

SELECT RTRIM(XMLAGG(XMLELEMENT(E,colname,',').EXTRACT('//text()') ORDER BY colname).GetClobVal(),',') AS LIST
FROM tablename;

Advantages of XMLAGG

The XMLAGG function has the following advantages:

• No line limit: XMLAGG stores concatenated values ​​as CLOBs (Character Large Objects) with no line limit.

Example usage

Consider the following code snippet:

SELECT SESSION_DT, C_IP, CS_USER_AGENT,
listagg(WEB_LINK, ' ')
WITHIN GROUP(ORDER BY C_IP, CS_USER_AGENT) "WEB_LINKS"
FROM webviews
GROUP BY C_IP, CS_USER_AGENT, SESSION_DT
ORDER BY SESSION_DT

To resolve errors encountered, LISTAGG can be replaced with XMLAGG:

SELECT SESSION_DT, C_IP, CS_USER_AGENT,
RTRIM(XMLAGG(XMLELEMENT(E,WEB_LINK,',').EXTRACT('//text()') ORDER BY WEB_LINK).GetClobVal(),',') AS "WEB_LINKS"
FROM webviews
GROUP BY C_IP, CS_USER_AGENT, SESSION_DT
ORDER BY SESSION_DT

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