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

Resolving Oracle's "Result of String Concatenation is Too Long" Error with LISTAGG

Oracle's LISTAGG function, while useful for string concatenation, can throw a "result of string concatenation is too long" error if the combined string exceeds the database's length limit. This limit varies based on the Oracle version and configuration.

This problem arises when attempting to concatenate values, for example, from a "WEB_LINK" column, grouped by other columns like "C_IP" and "CS_USER_AGENT". The resulting concatenated string might simply be too large for LISTAGG to handle.

A Superior Solution: Leveraging XMLAGG

XMLAGG provides a robust alternative to LISTAGG, capable of handling significantly larger concatenated strings. XMLAGG aggregates data into a structured XML format. The following SQL query demonstrates its application:

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

This query constructs a comma-separated list stored as a CLOB (Character Large Object), a data type with virtually unlimited length. The RTRIM function removes any trailing commas. The resulting LIST column contains the concatenated values.

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