Implementing select top N in Oracle:
Since Oracle does not support the select top statement, the combination of order by and rownum is often used in Oracle
to implement the query of select top n.
Simply put, the implementation method is as follows:
select column name 1 ... column name n from
(
select column name 1 ... column name n
from table name order by column name 1
)
where rownum <= N (the number of records extracted )
order by rownum asc
如：select id,name from (select id,name from student order by name) where rownum<=10 order by rownum asc
Sort by name and extract the top ten data
Attachment: The method of taking 100-150 pieces of data
1. Best option: use analytic functions
row_number() over ( partition by col1 order by col2 )
For example, if you want to take out 100-150 records, sort by tname
select tname, tabtype from (
select tname,tabtype,row_number() over ( order by tname ) rn from tab
) where rn between 100 and 150;
2. Use rownum virtual column
select tname,tabtype from (
select tname,tabtype,rownum rn from tab where rownum <= 150
) where rn >= 100;