Qualify和Having之间的区别

Question

有人能给我解释一下吗? Teradata中的qualify...over...partition by和group by...having有什么不同？

我也想知道他们的表现有没有什么不同。

Answer 1

QUALIFY是一个专有扩展，用于过滤窗口聚合函数的结果。

查询按照特定的顺序进行逻辑处理：

1. from : create the basic result set
2. 其中:从上一个结果集中删除行
3. GROUP BY:对上一个结果集应用聚合函数
4. 具有:从上一个结果集中删除行
5. OVER:在上一个结果集
6. 限定:从上一个结果集删除行

Answer 2

Having clause is used to filter the result set of the aggregate functions like (COUNT,min,max etc)
they eliminate rows based from groups based on some criteria like this :-
SELECT dept_no, MIN(salary), MAX(salary), AVG(salary)
     FROM employee
     WHERE dept_no IN (100,300,500,600)
     GROUP BY dept_no
     HAVING AVG(salary) > 37000;

The QUALIFY clause eliminates rows based on the function value, returning a new value for each of the participating rows.
It works on the final result set.

SELECT NAME,LOCATION FROM EMPLOYEE
 QUALIFY ROW_NUMBER() OVER ( PARTITION BY NAME ORDER BY JOINING_DATE DESC) = 1;


We can club both having and qualify as well in a query if we use both aggregate and analytical fucntion like below:-
SELECT StoreID, SUM(sale),
   SUM(profit) OVER (PARTITION BY StoreID)
   FROM facts
   GROUP BY StoreID, sale, profit
   HAVING SUM(sale) > 15
   QUALIFY SUM(profit) OVER (PARTITION BY StoreID) > 2;   



You can see there order of execution from dnoeth answer.