oracle row_number() over ,rank() over ,dense_rank() over ，keep 函数比较
create table test2 as
select 1 id, 111 mc,1 sl from dual union all
select 1 , 222,6 from dual union all
select 1 , 333,2 from dual union all
select 1 , 555,3 from dual union all
select 1 , 666,3 from dual union all
select 2 , 111,1 from dual union all
select 2 , 222,1 from dual union all
select 2 , 333,2 from dual union all
select 2 , 555,2 from dual
select t.* ,
row_number() over (partition by id order by t.sl) row_num,
rank() over (partition by id order by t.sl) rank,
dense_rank() over (partition by id order by t.sl) denserank
from test2 t
ID MC SL ROW_NUM RANK DENSERANK
---------- ---------- ---------- ---------- ---------- ----------
1 111 1 1 1 1
1 333 2 2 2 2
1 666 3 3 3 3
1 555 3 4 3 3
1 222 6 5 5 4
2 111 1 1 1 1
2 222 1 2 1 1
2 555 2 3 3 2
2 333 2 4 3 2
可知：
dense_rank在做排序时如果遇到列有重复值，则重复值所在行的序列值相同，而其后的序列值依旧递增，rank则是重复值所在行的序列值相同，但其后的序列值从+重复行数开始递增，而row_number则不管是否有重复行，(分组内)序列值始终递增
keep（dense_rank first/last order by ）
select id,mc,sl,
2 min(mc) keep(dense_rank first order by sl) over(partition by id) min_mc,
3 min(mc) keep(dense_rank last order by sl) over(partition by id) min_mc
4 from test2;
ID MC SL MIN_MC MIN_MC
---------- ---------- ---------- ---------- ----------
1 111 1 111 222
1 222 6 111 222
1 333 2 111 222
1 555 3 111 222
1 666 3 111 222
2 111 1 111 333
2 222 1 111 333
2 333 2 111 333
2 555 2 111 333
9 rows selected
转自:
http://blog.163.com/dykj_dxj/blog/static/2549252520108271158241/