题解 | #SQL255奇数行的first_name#

select ordered.first_name
from
    (SELECT tb.first_name,tb.rownum,row_number() over( order by tb.first_name) as rank_n
    from 
    (
        SELECT @row_n:=@row_n + 1 AS rownum,t.*
        FROM
        (SELECT first_name FROM employees) AS t,(select @row_n:=0) as r
    ) AS tb
    ) ordered
where ordered.rank_n % 2 = 1
order by ordered.rownum
;