spark-instrumented-optimizer/docs/sql-ref-syntax-qry-window.md

layout	title	displayTitle	license
global	Window Functions	Window Functions	Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Description

Window functions operate on a group of rows, referred to as a window, and calculate a return value for each row based on the group of rows. Window functions are useful for processing tasks such as calculating a moving average, computing a cumulative statistic, or accessing the value of rows given the relative position of the current row.

Syntax

{% highlight sql %} window_function OVER ( [ { PARTITION | DISTRIBUTE } BY partition_col_name = partition_col_val ( [ , ... ] ) ] { ORDER | SORT } BY expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [ , ... ] [ window_frame ] ) {% endhighlight %}

Parameters

window_function

• Ranking Functions

Syntax: RANK | DENSE_RANK | PERCENT_RANK | NTILE | ROW_NUMBER

• Analytic Functions

Syntax: CUME_DIST | LAG | LEAD

• Aggregate Functions

Syntax: MAX | MIN | COUNT | SUM | AVG | ...
Please refer to the Built-in Functions document for a complete list of Spark aggregate functions.

window_frame

Specifies which row to start the window on and where to end it.
Syntax:
{ RANGE | ROWS } { frame_start | BETWEEN frame_start AND frame_end }
If frame_end is omitted it defaults to CURRENT ROW.

frame_start and frame_end have the following syntax
Syntax:
UNBOUNDED PRECEDING | offset PRECEDING | CURRENT ROW | offset FOLLOWING | UNBOUNDED FOLLOWING
offset:specifies the offset from the position of the current row.

Examples

{% highlight sql %} CREATE TABLE employees (name STRING, dept STRING, salary INT, age INT);

INSERT INTO employees VALUES ("Lisa", "Sales", 10000, 35); INSERT INTO employees VALUES ("Evan", "Sales", 32000, 38); INSERT INTO employees VALUES ("Fred", "Engineering", 21000, 28); INSERT INTO employees VALUES ("Alex", "Sales", 30000, 33); INSERT INTO employees VALUES ("Tom", "Engineering", 23000, 33); INSERT INTO employees VALUES ("Jane", "Marketing", 29000, 28); INSERT INTO employees VALUES ("Jeff", "Marketing", 35000, 38); INSERT INTO employees VALUES ("Paul", "Engineering", 29000, 23); INSERT INTO employees VALUES ("Chloe", "Engineering", 23000, 25);

SELECT * FROM employees; +-----+-----------+------+-----+ | name| dept|salary| age| +-----+-----------+------+-----+ |Chloe|Engineering| 23000| 25| | Fred|Engineering| 21000| 28| | Paul|Engineering| 29000| 23| |Helen| Marketing| 29000| 40| | Tom|Engineering| 23000| 33| | Jane| Marketing| 29000| 28| | Jeff| Marketing| 35000| 38| | Evan| Sales| 32000| 38| | Lisa| Sales| 10000| 35| | Alex| Sales| 30000| 33| +-----+-----------+------+-----+

SELECT name, dept, RANK() OVER (PARTITION BY dept ORDER BY salary) AS rank FROM employees; +-----+-----------+------+----+ | name| dept|salary|rank| +-----+-----------+------+----+ | Lisa| Sales| 10000| 1| | Alex| Sales| 30000| 2| | Evan| Sales| 32000| 3| | Fred|Engineering| 21000| 1| | Tom|Engineering| 23000| 2| |Chloe|Engineering| 23000| 2| | Paul|Engineering| 29000| 4| |Helen| Marketing| 29000| 1| | Jane| Marketing| 29000| 1| | Jeff| Marketing| 35000| 3| +-----+-----------+------+----+

SELECT name, dept, DENSE_RANK() OVER (PARTITION BY dept ORDER BY salary ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS dense_rank FROM employees; +-----+-----------+------+----------+ | name| dept|salary|dense_rank| +-----+-----------+------+----------+ | Lisa| Sales| 10000| 1| | Alex| Sales| 30000| 2| | Evan| Sales| 32000| 3| | Fred|Engineering| 21000| 1| | Tom|Engineering| 23000| 2| |Chloe|Engineering| 23000| 2| | Paul|Engineering| 29000| 3| |Helen| Marketing| 29000| 1| | Jane| Marketing| 29000| 1| | Jeff| Marketing| 35000| 2| +-----+-----------+------+----------+

SELECT name, dept, age, CUME_DIST() OVER (PARTITION BY dept ORDER BY age RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS cume_dist FROM employees; +-----+-----------+------+------------------+ | name| dept|age | cume_dist| +-----+-----------+------+------------------+ | Alex| Sales| 33|0.3333333333333333| | Lisa| Sales| 35|0.6666666666666666| | Evan| Sales| 38| 1.0| | Paul|Engineering| 23| 0.25| |Chloe|Engineering| 25| 0.75| | Fred|Engineering| 28| 0.25| | Tom|Engineering| 33| 1.0| | Jane| Marketing| 28|0.3333333333333333| | Jeff| Marketing| 38|0.6666666666666666| |Helen| Marketing| 40| 1.0| +-----+-----------+------+------------------+

SELECT name, dept, salary, MIN(salary) OVER (PARTITION BY dept ORDER BY salary) AS min FROM employees; +-----+-----------+------+-----+ | name| dept|salary| min| +-----+-----------+------+-----+ | Lisa| Sales| 10000|10000| | Alex| Sales| 30000|10000| | Evan| Sales| 32000|10000| |Helen| Marketing| 29000|29000| | Jane| Marketing| 29000|29000| | Jeff| Marketing| 35000|29000| | Fred|Engineering| 21000|21000| | Tom|Engineering| 23000|21000| |Chloe|Engineering| 23000|21000| | Paul|Engineering| 29000|21000| +-----+-----------+------+-----+

SELECT name, salary, LAG(salary) OVER (PARTITION BY dept ORDER BY salary) AS lag, LEAD(salary, 1, 0) OVER (PARTITION BY dept ORDER BY salary) AS lead FROM employees; +-----+-----------+------+-----+-----+ | name| dept|salary| lag| lead| +-----+-----------+------+-----+-----+ | Lisa| Sales| 10000|NULL |30000| | Alex| Sales| 30000|10000|32000| | Evan| Sales| 32000|30000| 0| | Fred|Engineering| 21000| NULL|23000| |Chloe|Engineering| 23000|21000|23000| | Tom|Engineering| 23000|23000|29000| | Paul|Engineering| 29000|23000| 0| |Helen| Marketing| 29000| NULL|29000| | Jane| Marketing| 29000|29000|35000| | Jeff| Marketing| 35000|29000| 0| +-----+-----------+------+-----+-----+ {% endhighlight %}

Related Statements

• SELECT