Question

I need to get the next available id in a sequence, using GORM or native query.
How can I do this?

I’m using oracle.

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UPDATE:

I need this value BEFORE insert, because my row will use this value.
I have table called IMAGE, with column FILE_NAME, like this:

- ID | FILE_NAME
- 123 | foo_bar_123.png
- 124 | xxx_yyy_124.png

Tks a lot.

Answer 1

Why do you need the value before the insert? Could you get the information as part of the insert using the RETURNING clause, i.e.

INSERT INTO table_name( id, file_name )
  VALUES( some_sequence.nextval, <<bind variable>> )
  RETURNING id INTO <<bind variable>>

Or access it after the insert using

SELECT sequence_name.currval
  FROM dual

The currval of a sequence returns the most recent value of the sequence produced in the current session so it is actually thread-safe. Since sequences are designed to provide numbers in a highly concurrent environment, you cannot in general find out what the nextval is going to be unless you actually fetch the nextval. Even if you could, there is no guarantee that another thread won’t come along and get the value you peeked at before your INSERT took place so it wouldn’t be safe to peek at the nextval in a multi-user environment.