How to Reset an Oracle Sequence to Zero?

Resetting Oracle Sequences to Zero: A Practical Guide

Unlike PostgreSQL's straightforward ALTER SEQUENCE command, Oracle requires a workaround to reset a sequence to 0. This guide details a reliable method, adapted from Oracle expert Tom Kyte's approach.

The Procedure:

The following stored procedure effectively resets any Oracle sequence to a value of 0:

<code class="language-sql">create or replace procedure reset_seq(p_seq_name in varchar2)
is
    l_val number;
begin
    execute immediate 'select ' || p_seq_name || '.nextval from dual' INTO l_val;
    execute immediate 'alter sequence ' || p_seq_name || ' increment by -' || l_val || ' minvalue 0';
    execute immediate 'select ' || p_seq_name || '.nextval from dual' INTO l_val;
    execute immediate 'alter sequence ' || p_seq_name || ' increment by 1 minvalue 0';
end;
/</code>

How to Use It:

To reset a sequence called my_sequence to 0, simply run this command:

<code class="language-sql">execute reset_seq('my_sequence');</code>

Important Considerations:

• Performance: This procedure uses dynamic SQL, which might impact performance in high-volume environments.
• Alternatives: While other methods exist (like TRUNCATE TABLE or manual metadata updates), they often present limitations and potential risks. This procedure provides a safer and more reliable solution.

This method offers a robust and efficient way to manage Oracle sequences, ensuring data integrity and consistency.

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