您可以使用WINDOW關鍵字自定義窗口，為窗口函數自定義名稱。
命令格式
WINDOW <window_name> AS (<window_definition>)
[, <window_name> AS (<window_definition>)]
...window_name：必填。自定義某個窗口函數時，設置的自定義名稱（named window）。
window_definition：必填。被自定義名稱的窗口函數，窗口函數的介紹詳情請參見窗口函數。
使用限制
一個named window也可以用來定義另一個named window，經過這種定義，兩個named window的意義相同。未定義named window不允許用來定義另一個named window。
在同一個作用域中，不允許一個named window被多次定義。
示例數據
為便于理解各函數的使用方法，本文為您提供源數據，基于源數據提供函數相關示例。創建表emp，并添加數據，命令示例如下：
create table if not exists emp
(empno bigint,
ename string,
job string,
mgr bigint,
hiredate datetime,
sal bigint,
comm bigint,
deptno bigint);
tunnel upload emp.txt emp;emp.txt中的數據如下：
7369,SMITH,CLERK,7902,1980-12-17 00:00:00,800,,20
7499,ALLEN,SALESMAN,7698,1981-02-20 00:00:00,1600,300,30
7521,WARD,SALESMAN,7698,1981-02-22 00:00:00,1250,500,30
7566,JONES,MANAGER,7839,1981-04-02 00:00:00,2975,,20
7654,MARTIN,SALESMAN,7698,1981-09-28 00:00:00,1250,1400,30
7698,BLAKE,MANAGER,7839,1981-05-01 00:00:00,2850,,30
7782,CLARK,MANAGER,7839,1981-06-09 00:00:00,2450,,10
7788,SCOTT,ANALYST,7566,1987-04-19 00:00:00,3000,,20
7839,KING,PRESIDENT,,1981-11-17 00:00:00,5000,,10
7844,TURNER,SALESMAN,7698,1981-09-08 00:00:00,1500,0,30
7876,ADAMS,CLERK,7788,1987-05-23 00:00:00,1100,,20
7900,JAMES,CLERK,7698,1981-12-03 00:00:00,950,,30
7902,FORD,ANALYST,7566,1981-12-03 00:00:00,3000,,20
7934,MILLER,CLERK,7782,1982-01-23 00:00:00,1300,,10
7948,JACCKA,CLERK,7782,1981-04-12 00:00:00,5000,,10
7956,WELAN,CLERK,7649,1982-07-20 00:00:00,2450,,10
7956,TEBAGE,CLERK,7748,1982-12-30 00:00:00,1300,,10查詢數據如下：
SELECT * FROM emp;
--返回：
+------------+------------+------------+------------+------------+------------+------------+------------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+------------+------------+------------+------------+------------+------------+------------+------------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800 | NULL | 20|
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600 | 300 | 30|
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250 | 500 | 30|
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975 | NULL | 20|
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250 | 1400 | 30|
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850 | NULL | 30|
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450 | NULL | 10|
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000 | NULL | 20|
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000 | NULL | 10|
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500 | 0 | 30|
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100 | NULL | 20|
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950 | NULL | 30|
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000 | NULL | 20|
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300 | NULL | 10|
| 7948 | JACCKA | CLERK | 7782 | 1981-04-12 00:00:00 | 5000 | NULL | 10|
| 7956 | WELAN | CLERK | 7649 | 1982-07-20 00:00:00 | 2450 | NULL | 10|
| 7956 | TEBAGE | CLERK | 7748 | 1982-12-30 00:00:00 | 1300 | NULL | 10|
+------------+------------+------------+------------+------------+------------+------------+------------+使用示例
示例1：定義一個named window。
--沒有window關鍵字寫法 SELECT deptno, ename, sal, row_number() OVER (PARTITION BY deptno ORDER BY sal DESC) AS nums FROM emp; --返回： +------------+------------+------------+------------+ | deptno | ename | sal | nums | +------------+------------+------------+------------+ | 10 | JACCKA | 5000 | 1 | | 10 | KING | 5000 | 2 | | 10 | CLARK | 2450 | 3 | | 10 | WELAN | 2450 | 4 | | 10 | TEBAGE | 1300 | 5 | | 10 | MILLER | 1300 | 6 | | 20 | SCOTT | 3000 | 1 | | 20 | FORD | 3000 | 2 | | 20 | JONES | 2975 | 3 | | 20 | ADAMS | 1100 | 4 | | 20 | SMITH | 800 | 5 | | 30 | BLAKE | 2850 | 1 | | 30 | ALLEN | 1600 | 2 | | 30 | TURNER | 1500 | 3 | | 30 | MARTIN | 1250 | 4 | | 30 | WARD | 1250 | 5 | | 30 | JAMES | 950 | 6 | +------------+------------+------------+------------+ --有window關鍵字寫法 SELECT deptno, ename, sal, row_number() OVER w1 AS nums FROM emp WINDOW w1 AS (PARTITION BY deptno ORDER BY sal DESC); --返回相同： +------------+------------+------------+------------+ | deptno | ename | sal | nums | +------------+------------+------------+------------+ | 10 | JACCKA | 5000 | 1 | | 10 | KING | 5000 | 2 | | 10 | CLARK | 2450 | 3 | | 10 | WELAN | 2450 | 4 | | 10 | TEBAGE | 1300 | 5 | | 10 | MILLER | 1300 | 6 | | 20 | SCOTT | 3000 | 1 | | 20 | FORD | 3000 | 2 | | 20 | JONES | 2975 | 3 | | 20 | ADAMS | 1100 | 4 | | 20 | SMITH | 800 | 5 | | 30 | BLAKE | 2850 | 1 | | 30 | ALLEN | 1600 | 2 | | 30 | TURNER | 1500 | 3 | | 30 | MARTIN | 1250 | 4 | | 30 | WARD | 1250 | 5 | | 30 | JAMES | 950 | 6 | +------------+------------+------------+------------+示例2：同時定義多個named window。使用方式如下。
SELECT deptno, ename, max(sal) OVER w2 AS max_sal, row_number() OVER w1 AS nums FROM emp WINDOW w1 AS (PARTITION BY deptno ORDER BY sal DESC), w2 AS (PARTITION BY deptno);示例3：使用window語句在全局定義named window。
WINDOW w1 AS (PARTITION BY deptno ORDER BY sal DESC); INSERT OVERWRITE TABLE table1 SELECT row_number() OVER w1 AS nums FROM table2; INSERT OVERWRITE TABLE table3 SELECT max(column1) OVER w1 AS nums FROM table4;示例4：一個named window用來定義另一個named window。使用方式如下。
SELECT deptno, ename, max(sal) OVER w2 AS max_sal, row_number() OVER w1 AS nums FROM emp WINDOW w1 AS (PARTITION BY deptno ORDER BY sal DESC), w2 AS w1;說明經過這種定義，兩個named window的意義相同。
示例5（錯誤示例，用于提示）：未定義named window不允許用來定義另一個named window，以下為錯誤示例，其中W1和W2均未被定義。
SELECT deptno, ename, row_number() OVER w1 AS nums FROM emp WINDOW w1 AS w2;示例6（錯誤示例，用于提示）：在同一個作用域中，不允許一個named window被多次定義。以下為錯誤示例，其中W1被重復定義。
SELECT deptno, ename, row_number() OVER w1 AS nums FROM emp WINDOW w1 AS (PARTITION BY deptno ORDER BY sal DESC), w1 AS (PARTITION BY ename ORDER BY sal DESC);
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