Oracle uses increment to implement ID self-increase ____oracle

I know Oracle does not support auto_increment automatically increment, need to establish a sequence to achieve automatic increment.

Then set up a trigger to implement the Add 1 function.

The function that I want to implement is to add a piece of data to the Task table and add information to the Task scope table (the added information includes:

Task ID, channel ID)

I implement this in one method:

Steps:

1, to the Task table to add a task;

2, take out the ID of this task;

3, the task ID and channel ID added to the Task scope table;

The problem arises: if the ID in the task table is 1, the task ID in the scope table is not 1, but 2.

I am configured to increment is indeed correct, why.

about Oracle Implementation ID process which Oracle Master can give a clear description? Thank you.