Question

Is there an SQL instruction to retrieve the value of a sequence that does not increment it.

Thanks.

EDIT AND CONCLUSION

As stated by Justin Cave It’s not useful to try to “save” sequence number so

select a_seq.nextval from dual;

is good enough to check a sequence value.

I still keep Ollie answer as the good one because it answered the initial question. but ask yourself about the necessity of not modifying the sequence if you ever want to do it.

Answer 1

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

You can get a variety of sequence metadata from user_sequences, all_sequences and dba_sequences.

These views work across sessions.

EDIT:

If the sequence is in your default schema then:

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

If you want all the metadata then:

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

EDIT2:

A long winded way of doing it more reliably if your cache size is not 1 would be:

SELECT increment_by I
  FROM user_sequences
 WHERE sequence_name = 'SEQ';

      I
-------
      1

SELECT seq.nextval S
  FROM dual;

      S
-------
   1234

-- Set the sequence to decrement by 
-- the same as its original increment
ALTER SEQUENCE seq 
INCREMENT BY -1;

Sequence altered.

SELECT seq.nextval S
  FROM dual;

      S
-------
   1233

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

Sequence altered.

Just beware that if others are using the sequence during this time – they (or you) may get

ORA-08004: sequence SEQ.NEXTVAL goes below the sequences MINVALUE and cannot be instantiated

Also, you might want to set the cache to NOCACHE prior to the resetting and then back to its original value afterwards to make sure you’ve not cached a lot of values.