How to Retrieve Complete CLOB Data from Oracle Tables without ORA-06502 Errors?

Retrieving CLOB Data with Oracle Queries

While querying a table containing CLOB (Character Large OBject) columns, it's common to encounter values simply displayed as "(CLOB)" instead of the actual data. To retrieve the CLOB content, a solution is required.

DBMS_LOB.substr() Method

DBMS_LOB.substr() function is typically used for extracting portions of CLOB data. However, using this method may result in the error "ORA-06502" if the buffer size is too small to accommodate the data.

Solution: Specify Buffer Size

To overcome this error, it's necessary to specify a larger buffer size as an argument to the DBMS_LOB.substr() function. This ensures that sufficient space is allocated to store the retrieved data. Consider the following example:

SELECT DBMS_LOB.substr(myColumn, 3000) FROM myTable

In this example, the buffer size is set to 3000 characters, allowing for a substantial portion of the CLOB data to be retrieved. The retrieved data will be displayed as the output of the query.

By specifying a buffer size large enough to accommodate the data, you can successfully query CLOB columns and obtain the actual content.

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