### 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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Description
The SORT BY
clause is used to return the result rows sorted
within each partition in the user specified order. When there is more than one partition
SORT BY
may return result that is partially ordered. This is different
than ORDER BY clause which guarantees a
total order of the output.
Syntax
{% highlight sql %} SORT BY { expression [ sort_direction | nulls_sort_order ] [ , ... ] } {% endhighlight %}
Parameters
SORT BY
-
Specifies a comma-separated list of expressions along with optional parameters
sort_direction
andnulls_sort_order
which are used to sort the rows within each partition. 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 (zip_code INT, name STRING, age INT); INSERT INTO person VALUES (94588, 'Zen Hui', 50), (94588, 'Dan Li', 18), (94588, 'Anil K', 27), (94588, 'John V', NULL), (94511, 'David K', 42), (94511, 'Aryan B.', 18), (94511, 'Lalit B.', NULL);
-- Use REPARTITION
hint to partition the data by zip_code
to
-- examine the SORT BY
behavior. This is used in rest of the
-- examples.
-- Sort rows by name
within each partition in ascending manner
SELECT /*+ REPARTITION(zip_code) */ name, age, zip_code FROM person SORT BY name;
+--------+----+--------+
| name| age|zip_code|
+--------+----+--------+
| Anil K| 27| 94588|
| Dan Li| 18| 94588|
| John V|null| 94588|
| Zen Hui| 50| 94588|
|Aryan B.| 18| 94511|
| David K| 42| 94511|
|Lalit B.|null| 94511|
+--------+----+--------+
-- Sort rows within each partition using column position. SELECT /*+ REPARTITION(zip_code) */ name, age, zip_code FROM person SORT BY 1; +--------+----+--------+ | name| age|zip_code| +--------+----+--------+ | Anil K| 27| 94588| | Dan Li| 18| 94588| | John V|null| 94588| | Zen Hui| 50| 94588| |Aryan B.| 18| 94511| | David K| 42| 94511| |Lalit B.|null| 94511| +--------+----+--------+
-- Sort rows within partition in ascending manner keeping null values to be last. SELECT /*+ REPARTITION(zip_code) */ age, name, zip_code FROM person SORT BY age NULLS LAST; +----+--------+--------+ | age| name|zip_code| +----+--------+--------+ | 18| Dan Li| 94588| | 27| Anil K| 94588| | 50| Zen Hui| 94588| |null| John V| 94588| | 18|Aryan B.| 94511| | 42| David K| 94511| |null|Lalit B.| 94511| +----+--------+--------+
-- Sort rows by age within each partition in descending manner, which defaults to NULL LAST. SELECT /*+ REPARTITION(zip_code) */ age, name, zip_code FROM person SORT BY age DESC; +----+--------+--------+ | age| name|zip_code| +----+--------+--------+ | 50| Zen Hui| 94588| | 27| Anil K| 94588| | 18| Dan Li| 94588| |null| John V| 94588| | 42| David K| 94511| | 18|Aryan B.| 94511| |null|Lalit B.| 94511| +----+--------+--------+
-- Sort rows by age within each partition in descending manner keeping null values to be first. SELECT /*+ REPARTITION(zip_code) */ age, name, zip_code FROM person SORT BY age DESC NULLS FIRST; +----+--------+--------+ | age| name|zip_code| +----+--------+--------+ |null| John V| 94588| | 50| Zen Hui| 94588| | 27| Anil K| 94588| | 18| Dan Li| 94588| |null|Lalit B.| 94511| | 42| David K| 94511| | 18|Aryan B.| 94511| +----+--------+--------+
-- Sort rows within each partition based on more than one column with each column having -- different sort direction. SELECT /*+ REPARTITION(zip_code) */ name, age, zip_code FROM person SORT BY name ASC, age DESC; +--------+----+--------+ | name| age|zip_code| +--------+----+--------+ | Anil K| 27| 94588| | Dan Li| 18| 94588| | John V|null| 94588| | Zen Hui| 50| 94588| |Aryan B.| 18| 94511| | David K| 42| 94511| |Lalit B.|null| 94511| +--------+----+--------+ {% endhighlight %}