db中top n和limit m. n的实现

db2中不支持top n和limit m, n语法，只能用db2自己的方式来实现

top n

SELECT * FROM table_name where *** order by field_name desc FETCH FIRST n ROW ONLY 

这样可以取出按field_name降序排列的top n条记录

limit m,n

select * from (select *,ROW_NUMBER() OVER (order by field_name desc) AS RN from table_name where ***) as col where RN between m and n