Oracle database errors can be a nuisance, but with the right approach, you can resolve them quickly and efficiently. In this guide, we will focus on the ORA-01489 error, which occurs when the result of a string concatenation operation is too large for the target column. We will provide a step-by-step solution to fix this error and answer some frequently asked questions.
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Understanding the ORA-01489 Error
The ORA-01489 error occurs when the result of a string concatenation operation exceeds the maximum length allowed by the VARCHAR2, NVARCHAR2, or CLOB data type. In Oracle, the maximum length for VARCHAR2 and NVARCHAR2 is 4000 bytes, while for CLOB, it is 4 GB.
ORA-01489: result of string concatenation is too long
The error is caused when you try to concatenate two or more strings, and the resulting string length exceeds the allowed limit.
Consider the following example where you are trying to concatenate two strings with a length of 3000 each:
SELECT 'A string of 3000 characters...' || 'Another string of 3000 characters...' FROM DUAL;
In this case, the resulting string will have a length of 6000 characters, which is more than the maximum allowed length for VARCHAR2 and NVARCHAR2.
How to Fix ORA-01489 Error
To fix the ORA-01489 error, you can use one of the following methods:
Method 1: Use SUBSTR function
Use the SUBSTR function to limit the length of the concatenated strings to the maximum allowed length.
SELECT SUBSTR('A string of 3000 characters...', 1, 2000) || SUBSTR('Another string of 3000 characters...', 1, 2000) FROM DUAL;
In this example, we limit the length of each string to 2000 characters, ensuring that the concatenated string does not exceed the maximum length.
Method 2: Use a CLOB column
If you need to store large strings, you can use a CLOB column instead of VARCHAR2 or NVARCHAR2.
CREATE TABLE large_strings (id NUMBER, long_string CLOB);
Now you can insert large strings into the
large_strings table without encountering the ORA-01489 error:
INSERT INTO large_strings (id, long_string) VALUES (1, 'A string of 3000 characters...' || 'Another string of 3000 characters...');
Q1: Can I increase the maximum length of VARCHAR2 or NVARCHAR2 in Oracle?
No, the maximum length of VARCHAR2 and NVARCHAR2 in Oracle is 4000 bytes, and it cannot be increased. However, you can use the CLOB data type to store larger strings.
Q2: Can I use the CONCAT function instead of the || operator to avoid the ORA-01489 error?
No, using the CONCAT function will still result in the same error if the concatenated string exceeds the maximum allowed length. You should use one of the methods mentioned in this guide to fix the error.
Q3: How can I check the length of a string in Oracle?
You can use the LENGTH function to check the length of a string in Oracle.
SELECT LENGTH('A string of 3000 characters...') FROM DUAL;
Q4: How can I concatenate strings without exceeding the maximum length?
You can use the SUBSTR function to limit the length of each string before concatenating them, as shown in Method 1.
Q5: Can I use the same methods to fix the ORA-01489 error in PL/SQL?
Yes, you can use the same methods to fix the ORA-01489 error in PL/SQL. Just make sure to use the appropriate syntax for PL/SQL.
Note: The examples in this guide were tested on Oracle Database 19c, but they should also work on other versions of Oracle Database.