sql常用函数

1.row_number函数，排名连续不重复，搭配over()使用，需要注意over字句与外面的order by字段，顺序需一致。

select age, row_number() over() from table

select age, row_number() over(order by age) from table order by age

2.rank函数，排名不连续，会根据排序的字段将相同的值归为一组。

select age,rank() over(order by age) from table order by age

3.dense_rank函数，排名连续，会根据排序的字段将相同的值归为一组。

select age,dense_rank() over(order by age) from table order by age

4.ntile函数，将所有记录分成n个组，每组序号一样

select age,ntile(2) over(order by age) from table order by age