PERCENTILE_CONT

PERCENTILE_CONT ( <expression1> )
WITHIN GROUP ( ORDER BY <expression2> [ ASC | DESC ] )

PERCENTILE_CONT和PERCENTILE_DISC都是为了计算百分位的数值，比如计算在某个百分位时某个栏位的数值是多少。他们的区别就是前者是连续型，后者是离散型。CONT代表continuous，DISC代表discrete。PERCENTILE_CONT是连续型意味它考虑的是区间，所以值是绝对的中间值。而PERCENTILE_DISC是离散型，所以它更多考虑向上或者向下取舍，而不会考虑区间。

示例
以下示例使用 PERCENTILE_CONT 函数来确定某区域汽车销售量的第 10 个百分点值。

示例中使用了以下数据集：

sales       region        dealer_name
900         Northeast     Boston
800         Northeast     Worcester
800         Northeast     Providence
700         Northeast     Lowell
540         Northeast     Natick
500         Northeast     New Haven
450         Northeast     Hartford
800         Northwest     SF
600         Northwest     Seattle
500         Northwest     Portland
400         Northwest     Dublin
500         South         Houston
400         South         Austin
300         South         Dallas
200         South         Dover

SELECT region, PERCENTILE_CONT(0.1)
WITHIN GROUP ( ORDER BY sales DESC )
FROM carSales GROUP BY region;

SELECT 语句的结果列出了某区域汽车销售量的第 10 个百分点值，ORDER BY后面跟的是column name