### 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>
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global | ORDER BY Clause | ORDER 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 ORDER BY
clause is used to return the result rows in a sorted manner
in the user specified order. Unlike the SORT BY
clause, this clause guarantees a total order in the output.
Syntax
{% highlight sql %} ORDER BY { expression [ sort_direction | nulls_sort_oder ] [ , ... ] } {% endhighlight %}
Parameters
ORDER BY
-
Specifies a comma-separated list of expressions along with optional parameters
sort_direction
andnulls_sort_order
which are used to sort the rows. sort_direction
-
Optionally specifies whether to sort the rows in ascending or descending
order. The valid values for the sort direction are
ASC
for ascending andDESC
for descending. If sort direction is not explicitly specified, then by default rows are sorted ascending.
Syntax:[ ASC | DESC ]
nulls_sort_order
-
Optionally specifies whether NULL values are returned before/after non-NULL values. If
null_sort_order
is not specified, then NULLs sort first if sort order isASC
and NULLS sort last if sort order isDESC
.
- If
NULLS FIRST
is specified, then NULL values are returned first regardless of the sort order. - If
NULLS LAST
is specified, then NULL values are returned last regardless of the sort order.
Syntax:[ NULLS { FIRST | LAST } ]
- If
Examples
{% highlight sql %} CREATE TABLE person (id INT, name STRING, age INT); INSERT INTO person VALUES (100, 'John', 30), (200, 'Mary', NULL), (300, 'Mike', 80), (400, 'Jerry', NULL), (500, 'Dan', 50);
-- Sort rows by age. By default rows are sorted in ascending manner with NULL FIRST. SELECT name, age FROM person ORDER BY age; +-----+----+ | name| age| +-----+----+ |Jerry|null| | Mary|null| | John| 30| | Dan| 50| | Mike| 80| +-----+----+
-- Sort rows in ascending manner keeping null values to be last. SELECT name, age FROM person ORDER BY age NULLS LAST; +-----+----+ | name| age| +-----+----+ | John| 30| | Dan| 50| | Mike| 80| | Mary|null| |Jerry|null| +-----+----+
-- Sort rows by age in descending manner, which defaults to NULL LAST. SELECT name, age FROM person ORDER BY age DESC; +-----+----+ | name| age| +-----+----+ | Mike| 80| | Dan| 50| | John| 30| |Jerry|null| | Mary|null| +-----+----+
-- Sort rows in ascending manner keeping null values to be first. SELECT name, age FROM person ORDER BY age DESC NULLS FIRST; +-----+----+ | name| age| +-----+----+ |Jerry|null| | Mary|null| | Mike| 80| | Dan| 50| | John| 30| +-----+----+
-- Sort rows based on more than one column with each column having different -- sort direction. SELECT * FROM person ORDER BY name ASC, age DESC; +---+-----+----+ | id| name| age| +---+-----+----+ |500| Dan| 50| |400|Jerry|null| |100| John| 30| |200| Mary|null| |300| Mike| 80| +---+-----+----+ {% endhighlight %}