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sql-ref-syntax-qry-select-distribute-by.md

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DISTRIBUTE BY Clause
DISTRIBUTE BY Clause
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

The DISTRIBUTE BY clause is used to repartition the data based on the input expressions. Unlike the CLUSTER BY clause, this does not sort the data within each partition.

Syntax

DISTRIBUTE BY { expression [ , ... ] }

Parameters

  • expression

    Specifies combination of one or more values, operators and SQL functions that results in a value.

Examples

CREATE TABLE person (name STRING, age INT);
INSERT INTO person VALUES
    ('Zen Hui', 25),
    ('Anil B', 18),
    ('Shone S', 16),
    ('Mike A', 25),
    ('John A', 18),
    ('Jack N', 16);

-- Reduce the number of shuffle partitions to 2 to illustrate the behavior of `DISTRIBUTE BY`.
-- It's easier to see the clustering and sorting behavior with less number of partitions.
SET spark.sql.shuffle.partitions = 2;

-- Select the rows with no ordering. Please note that without any sort directive, the result
-- of the query is not deterministic. It's included here to just contrast it with the
-- behavior of `DISTRIBUTE BY`. The query below produces rows where age columns are not
-- clustered together.
SELECT age, name FROM person;
+---+-------+
|age|   name|
+---+-------+
| 16|Shone S|
| 25|Zen Hui|
| 16| Jack N|
| 25| Mike A|
| 18| John A|
| 18| Anil B|
+---+-------+

-- Produces rows clustered by age. Persons with same age are clustered together.
-- Unlike `CLUSTER BY` clause, the rows are not sorted within a partition.
SELECT age, name FROM person DISTRIBUTE BY age;
+---+-------+
|age|   name|
+---+-------+
| 25|Zen Hui|
| 25| Mike A|
| 18| John A|
| 18| Anil B|
| 16|Shone S|
| 16| Jack N|
+---+-------+

Related Statements