How Can I Retrieve Oracle Sequence Values Without Incrementing the Counter?

Retrieving Sequence Values Without Incrementing in Oracle

When retrieving sequence values in Oracle, a common question is whether it's possible to do so without incrementing the sequence. This article explores the available options to address this scenario.

Using All_Sequences View

The All_sequences view provides a way to obtain the last assigned value for a sequence without incrementing it:

SELECT last_number
FROM all_sequences
WHERE sequence_owner = '<sequence owner>'
AND sequence_name = '<sequence_name>';

This query retrieves the last assigned value of the specified sequence. However, it's important to note that the all_sequences view is session specific, so the result may differ from the actual current value if other sessions have been using the sequence.

Additional Information and Considerations

• For sequences in the default schema, the user_sequences view can be used instead of all_sequences.
• To get comprehensive sequence metadata, including the last assigned value, use the following query:

SELECT *
FROM user_sequences
WHERE sequence_name = '<sequence_name>';

• If the sequence cache size is not 1, you can use a more involved approach to reliably retrieve the current value without incrementing it. This involves temporarily decrementing the sequence increment, retrieving the value, and resetting the increment:

-- First determine the sequence increment
SELECT increment_by I
FROM user_sequences
WHERE sequence_name = 'SEQ';

-- Retrieve the sequence value
SELECT seq.nextval S
FROM dual;

-- Decrement the sequence increment
ALTER SEQUENCE seq 
INCREMENT BY -1;

-- Retrieve the previous sequence value again
SELECT seq.nextval S
FROM dual;

-- Reset the sequence increment
ALTER SEQUENCE seq 
INCREMENT BY 1;

This approach ensures that the current value is retrieved without modifying the sequence. However, it should be used with caution in multi-user environments where other processes may be using the sequence.

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