179289f0bf
### What changes were proposed in this pull request? This PR intends to clean up the SQL documents in `doc/sql-ref*`. Main changes are as follows; - Fixes wrong syntaxes and capitalize sub-titles - Adds some DDL queries in `Examples` so that users can run examples there - Makes query output in `Examples` follows the `Dataset.showString` (right-aligned) format - Adds/Removes spaces, Indents, or blank lines to follow the format below; ``` --- license... --- ### Description Writes what's the syntax is. ### Syntax {% highlight sql %} SELECT... WHERE... // 4 indents after the second line ... {% endhighlight %} ### Parameters <dl> <dt><code><em>Param Name</em></code></dt> <dd> Param Description </dd> ... </dl> ### Examples {% highlight sql %} -- It is better that users are able to execute example queries here. -- So, we prepare test data in the first section if possible. CREATE TABLE t (key STRING, value DOUBLE); INSERT INTO t VALUES ('a', 1.0), ('a', 2.0), ('b', 3.0), ('c', 4.0); -- query output has 2 indents and it follows the `Dataset.showString` -- format (right-aligned). SELECT * FROM t; +---+-----+ |key|value| +---+-----+ | a| 1.0| | a| 2.0| | b| 3.0| | c| 4.0| +---+-----+ -- Query statements after the second line have 4 indents. SELECT key, SUM(value) FROM t GROUP BY key; +---+----------+ |key|sum(value)| +---+----------+ | c| 4.0| | b| 3.0| | a| 3.0| +---+----------+ ... {% endhighlight %} ### Related Statements * [XXX](xxx.html) * ... ``` ### Why are the changes needed? The most changes of this PR are pretty minor, but I think the consistent formats/rules to write documents are important for long-term maintenance in our community ### Does this PR introduce any user-facing change? Yes. ### How was this patch tested? Manually checked. Closes #28151 from maropu/MakeRightAligned. Authored-by: Takeshi Yamamuro <yamamuro@apache.org> Signed-off-by: Sean Owen <srowen@gmail.com>
100 lines
3.1 KiB
Markdown
100 lines
3.1 KiB
Markdown
---
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layout: global
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title: DISTRIBUTE BY Clause
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displayTitle: DISTRIBUTE BY Clause
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license: |
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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---
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### Description
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The <code>DISTRIBUTE BY</code> clause is used to repartition the data based
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on the input expressions. Unlike the [CLUSTER BY](sql-ref-syntax-qry-select-clusterby.html)
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clause, this does not sort the data within each partition.
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### Syntax
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{% highlight sql %}
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DISTRIBUTE BY { expression [ , ... ] }
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{% endhighlight %}
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### Parameters
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<dl>
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<dt><code><em>expression</em></code></dt>
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<dd>
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Specifies combination of one or more values, operators and SQL functions that results in a value.
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</dd>
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</dl>
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### Examples
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{% highlight sql %}
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CREATE TABLE person (name STRING, age INT);
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INSERT INTO person VALUES
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('Zen Hui', 25),
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('Anil B', 18),
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('Shone S', 16),
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('Mike A', 25),
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('John A', 18),
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('Jack N', 16);
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-- Reduce the number of shuffle partitions to 2 to illustrate the behavior of `DISTRIBUTE BY`.
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-- It's easier to see the clustering and sorting behavior with less number of partitions.
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SET spark.sql.shuffle.partitions = 2;
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-- Select the rows with no ordering. Please note that without any sort directive, the result
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-- of the query is not deterministic. It's included here to just contrast it with the
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-- behavior of `DISTRIBUTE BY`. The query below produces rows where age columns are not
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-- clustered together.
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SELECT age, name FROM person;
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+---+-------+
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|age| name|
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+---+-------+
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| 16|Shone S|
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| 25|Zen Hui|
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| 16| Jack N|
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| 25| Mike A|
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| 18| John A|
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| 18| Anil B|
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+---+-------+
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-- Produces rows clustered by age. Persons with same age are clustered together.
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-- Unlike `CLUSTER BY` clause, the rows are not sorted within a partition.
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SELECT age, name FROM person DISTRIBUTE BY age;
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+---+-------+
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|age| name|
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+---+-------+
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| 25|Zen Hui|
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| 25| Mike A|
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| 18| John A|
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| 18| Anil B|
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| 16|Shone S|
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| 16| Jack N|
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+---+-------+
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{% endhighlight %}
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### Related Statements
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* [SELECT Main](sql-ref-syntax-qry-select.html)
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* [WHERE Clause](sql-ref-syntax-qry-select-where.html)
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* [GROUP BY Clause](sql-ref-syntax-qry-select-groupby.html)
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* [HAVING Clause](sql-ref-syntax-qry-select-having.html)
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* [ORDER BY Clause](sql-ref-syntax-qry-select-orderby.html)
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* [SORT BY Clause](sql-ref-syntax-qry-select-sortby.html)
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* [CLUSTER BY Clause](sql-ref-syntax-qry-select-clusterby.html)
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* [LIMIT Clause](sql-ref-syntax-qry-select-limit.html)
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