oracle row_number() rank() dense_rank()区别，备忘笔记

经常用经常忘的东西，做个笔记。

• row_number 连续
• rank 并列跳过
• dense_rank 并列不跳过

sql：

	with tab as (
	select 1 a from dual
	union all
	select 2 a from dual
	union all
	select 2 a from dual
	union all
	select 3 a from dual
	)
	select a,
	       row_number() over(order by a) row_number,
	       rank() over(order by a) rank,
	       dense_rank() over(order by a) dense_rank
	  from tab;

A	ROW_NUMBER	RANK	DENSE_RANK
1	1	1	1
2	2	2	2
2	3	2	2
3	4	4	3

一图流，不解释。