This guide will help you understand and resolve the Oracle error ORA-00997, which occurs due to the illegal use of the LONG datatype. We will cover the causes of this error and provide step-by-step solutions to fix it. By the end of this guide, you should be able to resolve the ORA-00997 error and prevent it from occurring in the future.
Table of Contents
Understanding the ORA-00997 Error
The ORA-00997 error occurs when an illegal use of the LONG datatype is detected in an Oracle database. The LONG datatype is used to store variable-length character strings with a maximum length of two gigabytes. However, Oracle has deprecated the LONG datatype in favor of LOB (Large Object) datatypes, such as CLOB and BLOB.
The error message for ORA-00997 looks like this:
ORA-00997: illegal use of LONG datatype
Causes of ORA-00997 Error
There are two main causes for the ORA-00997 error:
Using LONG datatype in a SELECT statement with a DISTINCT clause or a GROUP BY clause: Oracle does not support the use of LONG columns in SELECT statements with DISTINCT or GROUP BY clauses.
Using LONG datatype with a function: Oracle does not allow LONG columns to be used as arguments to functions or in expressions.
Step-by-Step Guide to Fix ORA-00997 Error
To resolve the ORA-00997 error, you can either use the LONG RAW datatype or convert the LONG datatype to a LOB datatype.
Solution 1: Use LONG RAW Datatype
If you need to work with raw binary data, you can use the LONG RAW datatype instead of the LONG datatype. However, this solution is not recommended, as both LONG and LONG RAW are deprecated in favor of LOB datatypes.
Solution 2: Convert LONG to LOB
Converting the LONG datatype to a LOB datatype, such as CLOB or BLOB, is the recommended solution. Here are the steps to convert LONG to LOB:
Create a new LOB column: Add a new column with the LOB datatype to the table containing the LONG column. For example, if you have a table called my_table with a LONG column called long_column, you can add a new CLOB column called clob_column using the following SQL statement:
ALTER TABLE my_table ADD (clob_column CLOB);
Copy the data from the LONG column to the LOB column: Use the DBMS_LOB.CONVERTTOCLOB function to copy the data from the LONG column to the LOB column. You can use a PL/SQL block to perform this operation:
DECLARE
cursor c1 is SELECT long_column, clob_column, ROWID FROM my_table FOR UPDATE;
v_long LONG;
v_clob CLOB;
v_rowid ROWID;
BEGIN
FOR rec in c1 LOOP
v_long := rec.long_column;
v_clob := TO_LOB(v_long);
v_rowid := rec.ROWID;
UPDATE my_table SET clob_column = v_clob WHERE ROWID = v_rowid;
END LOOP;
COMMIT;
END;
/
Drop the LONG column: After copying the data to the LOB column, you can drop the LONG column using the following SQL statement:
```sql
ALTER TABLE my_table DROP COLUMN long_column;
```
FAQs
Q1: What is the difference between LONG and LOB datatypes?
A: The LONG datatype is a deprecated datatype used to store variable-length character strings with a maximum length of two gigabytes. LOB (Large Object) datatypes, such as CLOB and BLOB, are the recommended replacements for LONG. LOB datatypes can store up to four gigabytes of data and provide better performance and functionality compared to LONG.
Q2: Can I use the LONG datatype in a SELECT statement with a DISTINCT clause or a GROUP BY clause?
A: No, Oracle does not support the use of LONG columns in SELECT statements with DISTINCT or GROUP BY clauses. To resolve this issue, you can convert the LONG datatype to a LOB datatype.
Q3: Can I use the LONG datatype with a function?
A: No, Oracle does not allow LONG columns to be used as arguments to functions or in expressions. To resolve this issue, you can convert the LONG datatype to a LOB datatype.
Q4: How do I convert a LONG RAW datatype to a BLOB datatype?
A: The process of converting a LONG RAW datatype to a BLOB datatype is similar to converting a LONG to a CLOB datatype. First, create a new BLOB column, copy the data from the LONG RAW column to the BLOB column using the DBMS_LOB.CONVERTTOBLOB function, and then drop the LONG RAW column.
Q5: How can I avoid the ORA-00997 error in the future?
A: To avoid the ORA-00997 error in the future, refrain from using the LONG datatype in your database schema. Instead, use LOB datatypes, such as CLOB and BLOB, which provide better performance and functionality compared to LONG.