PERCENT_RANK虽然也带有PERCENT，但是和前两个没有什么关系。它是为了计算当前值按百分比计算所处在百分位位置。
参考：
PERCENTILE_CONT (Transact-SQL)
PERCENTILE_DISC (Transact-SQL)
PERCENT_RANK (Transact-SQL)
SQL Server ->> PERCENTILE_CONT、PERCENTILE_DISC 和 PERCENT_RANK 函数
标签：
SQL Server ->> PERCENTILE_CONT、PERCENTILE_DISC 和 PERCENT_RANK 函数
AdventureWorks2012;
SELECT DISTINCT Name AS DepartmentName
,PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY ph.Rate)
OVER (PARTITION BY Name) AS MedianCont
,PERCENTILE_DISC(0.5) WITHIN GROUP (ORDER BY ph.Rate)
OVER (PARTITION BY Name) AS MedianDisc
FROM HumanResources.Department AS d
INNER JOIN HumanResources.EmployeeDepartmentHistory AS dh
ON dh.DepartmentID = d.DepartmentID
INNER JOIN HumanResources.EmployeePayHistory AS ph
ON ph.BusinessEntityID = dh.BusinessEntityID
WHERE dh.EndDate IS NULL;