Project: Apache Spark (App Definition and Development / Streaming & Messaging)
File: sql-ref-syntax-qry-select-window.md

layout: global title: Window Functions displayTitle: Window Functions license: | 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. 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. ```sql windowfunction [ nullsoption ] OVER ( [ { PARTITION | DISTRIBUTE } BY partitioncolname = partitioncolval ( [ , ... ] ) ] { ORDER | SORT } BY expression [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [ , ... ] [ window_frame ] ) ``` window_function* Ranking Functions Syntax: `RANK | DENSERANK | PERCENTRANK | NTILE | ROW_NUMBER` Analytic Functions Syntax: `CUMEDIST | LAG | LEAD | NTHVALUE | FIRSTVALUE | LASTVALUE` Aggregate Functions Syntax: `MAX | MIN | COUNT | SUM | AVG | ...` Please refer to the document for a complete list of Spark aggregate functions. nulls_option* Specifies whether or not to skip null values when evaluating the window function. `RESPECT NULLS` means not skipping null values, while `IGNORE NULLS` means skipping. If not specified, the default is `RESPECT NULLS`. Syntax: `{ IGNORE | RESPECT } NULLS` Note: Only `LAG | LEAD | NTHVALUE | FIRSTVALUE | LAST_VALUE` can be used with `IGNORE NULLS`. window_frame* Specifies which row to start the window on and where to end it. Syntax: `{ RANGE | ROWS } { framestart | BETWEEN framestart AND frame_end }` `framestart` and `frameend` 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. Note: If `frame_end` is omitted it defaults to `CURRENT

```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, salary, 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, salary, 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| +--+--++--+--+ SELECT id, v, LEAD(v, 0) IGNORE NULLS OVER w lead, LAG(v, 0) IGNORE NULLS OVER w lag, NTHVALUE(v, 2) IGNORE NULLS OVER w nthvalue, FIRSTVALUE(v) IGNORE NULLS OVER w firstvalue, LASTVALUE(v) IGNORE NULLS OVER w lastvalue FROM testignorenull WINDOW w AS (ORDER BY id) ORDER BY id; +--+-+-+-++--+-+ |id| v|lead| lag|nthvalue|firstvalue|last_value| +--+-+-+-++--+-+ | 0|NULL|NULL|NULL| NULL| NULL| NULL| | 1| x| x| x| NULL| x| x| | 2|NULL|NULL|NULL| NULL| x| x| | 3|NULL|NULL|NULL| NULL| x| x| | 4| y| y| y| y| x| y| | 5|NULL|NULL|NULL| y| x| y| | 6| z| z| z| y| x| z| | 7| v| v| v| y| x| v| | 8|NULL|NULL|NULL| y| x| v| +--+-+-+-++--+-+ ```