Oracle – errors

ORA-00001: unique constraint violated

The ORA-00001 message is triggered when a unique constraint has been violated. Essentially the user causes the error when trying to execute an INSERT or UPDATE statement that has generated a duplicate value in a restricted field. The error can commonly be found when a program attempts to insert a duplicate row in a table.

Before we progress to resolving the issue, it would be ideal to have some more information about the error. If you are unsure as to which constraint was violated to trigger the ORA-00001, there is an SQL statement that you can run to find out more about it. You can type the following command in:

SELECT DISTINCT table_name
FROM all_indexes
WHERE index_name = 'CONSTRAINT_NAME' ;

The constraint name can be found by looking at the error message itself. In parenthesis following the ORA-00001 notice, the constraint should be listed. This process will then return the name of the table that features the violated constraint.

Now that we know the constraint and table in question, we can move forward with fixing the problems itself. There are a few basic options. You can modify the SQL so that no duplicate values are created, thus no errors are triggered. If you do not wish to do this, you can also simply drop the table constraint altogether. This would only be recommended if the constraint is unnecessary for the foundation of your table.

Another option would be to modify the constraint so that it can allow duplicate values in your table. Depending on your version of Oracle, this can be done multiple ways. The first and universal method would be to manually adjust the constraint. However, if you’re using Oracle 11g or newer, you can use the ignore_row_on_dupkey_index hint. This feature will allow for insert SQL’s to enter as duplicates and be effectively ignored so that an ORA-00001 message will not be triggered.

By employing hints such as this, the ORA-00001 error can be sidestepped in many circumstances. A trigger method can also be a preventative approach to minimizing the frequency of ORA-00001 errors. These types of automatic increment columns can overwrite the value from an ID by inserting a value from the sequence in its place. 

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