Select top N with “for update skip locked” in Oracle

问题

In Oracle, I can select the top 1 message in a sorted table with

select messageid from(
    select 
        messageid, 
        RANK() over (order by messageid asc) as msg_rank 
    from messages
) where msg_rank=1;

And as I discovered in a previous question I can select a row exclusively with

select * from messages where rownum < 2 for update skip locked;

However I can't merge these two concepts together

select messageid from(
    select 
        messageid, 
        RANK() over (order by messageid asc) as msg_rank 
    from messages
) where msg_rank=1 for update skip locked;

-- results in error
-- ORA-02014: cannot select FOR UPDATE from view with DISTINCT, GROUP BY, etc.

How can I select the top N with readpast locking?

回答1:

Will this work?

select messageid from messages 
    where messageid in (
       select messageid from(
         select 
          messageid, 
          RANK() over (order by messageid asc) as msg_rank 
          from messages
       ) where msg_rank=1
    )
  for update skip locked;

来源：https://stackoverflow.com/questions/3939386/select-top-n-with-for-update-skip-locked-in-oracle