How to Resolve Oracle Error ORA-01489: Result of String Concatenation is Too Long?

Oracle Error ORA-01489: Result of String Concatenation is Too Long

This error typically occurs when the result of a string concatenation operation exceeds the maximum length limit set by Oracle. By default, this limit is 4000 bytes.

Root Cause:

The error message "ORA-01489: result of string concatenation is too long" directly indicates that the output of a concatenation operation is longer than the 4000 byte limit.

Solution:

There are several approaches to resolve this error:

1. XMLAGG Function:

XMLAGG allows you to concatenate values beyond the 4000 byte limit. Instead of using LISTAGG, you can use XMLAGG to combine multiple columns. For example:

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

2. Column Concatenation:

If you need to concatenate multiple columns with large values that exceed the 4000 byte limit, you can concatenate the XMLAGG output of each column:

SELECT ID,
       rtrim(xmlagg(XMLELEMENT(e,col1,',').EXTRACT('//text()') ).GetClobVal(), ',')
       || 
       rtrim(xmlagg(XMLELEMENT(e,col2,',').EXTRACT('//text()') ).GetClobVal(), ',') 
       AS very_long_text
FROM DATA
GROUP BY ID
ORDER BY ID;

Other Considerations:

• It's possible that the error is actually misleading, and the true cause may be a different issue, such as insufficient memory.
• Check the NLS_LENGTH_SEMANTICS database parameter. It determines how string concatenation length is calculated.
• Using functions like SUBSTR or TRIM may reduce the string length, but be careful not to truncate essential data.

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