The window function can be used in combination with GROUP BY. The rule is that the window range is valid for the following query results, so it doesn't really care whether GROUP BY is performed. Let's look at the following example: The cumulative aggregation after grouping by region is pe...
Conversely, the LAST_VALUE() function extracts the value of a specified column from the last row of a given window. FIRST_VALUE() and LAST_VALUE() over the Entire Result Set The following example uses FIRST_VALUE() and LAST_VALUE() to return all products and their first and last ...
With a window function, the original row remains intact. The partition is logical, and used only for calculation purposes. Here is a continuation of our previous example. In this case, we’ve partitioned the result by TerritoryID. SELECT BusinessEntityID ,TerritoryID ,SalesYTD ,SUM(SalesYTD...
Refer also to WINDOW Clause example 2 for a query showing this function used with the WINDOW clause.ROW_NUMBER() Description Returns a unique row number for every object in every window partition. In each window partition, the row numbering starts at 1. The window order clause determines the...
For details about each nonaggregate function, seeSection 14.20.1, “Window Function Descriptions”. As an example of one of those nonaggregate window functions, this query usesROW_NUMBER(), which produces the row number of each row within its partition. In this case, rows are numbered per co...
For example, if two rows are ranked 1, the next rank is 3. RANK differs from the DENSE_RANK window function in one respect: For DENSE_RANK, if two or more rows tie, there is no gap in the sequence of ranked values. For example, if two rows are ranked 1, the next rank is 2...
Each function uses the rows in the current frame, which, per the window definition shown, extends from the first partition row to the current row. For theNTH_VALUE()calls, the current frame does not always include the requested row; in such cases, the return value isNULL. ...
窗函数(window function)的计算方式与传统的单行和聚合不同 窗函数是在当前表中, 基于当前行的相关行的计算, 注意是基于多行的计算 属于一种聚合计算, 可以使用聚合类型的函数(aggregate function) 使用窗函数并不会导致结果的聚合, 也就是结果依然是当前的行结构 ...
In this example, we try to use the RANK() function in the WHERE clause to find the three students with the highest GPA, which leads to the following error in PostgreSQL (a similar occurs in MySQL and SQL Server): We can use a subquery or a common table expression (CTE) as a workar...
If you replace the 0.5 following the name of the function with another probability between 0 and 1, you will get the nth percentile. For example, 0.9 returns the 90th percentile. Each function examines the percent rank of the values in a partition until it finds the one that is equal to...