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>
5.3 KiB
| layout | title | displayTitle | license |
|---|---|---|---|
| global | DESCRIBE FUNCTION | DESCRIBE FUNCTION | 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
DESCRIBE FUNCTION statement returns the basic metadata information of an
existing function. The metadata information includes the function name, implementing
class and the usage details. If the optional EXTENDED option is specified, the basic
metadata information is returned along with the extended usage information.
Syntax
{% highlight sql %} { DESC | DESCRIBE } FUNCTION [ EXTENDED ] function_name {% endhighlight %}
Parameters
function_name-
Specifies a name of an existing function in the system. The function name may be
optionally qualified with a database name. If `function_name` is qualified with
a database then the function is resolved from the user specified database, otherwise
it is resolved from the current database.
Syntax:[ database_name. ] function_name
Examples
{% highlight sql %} -- Describe a builtin scalar function. -- Returns function name, implementing class and usage DESC FUNCTION abs; +-------------------------------------------------------------------+ |function_desc | +-------------------------------------------------------------------+ |Function: abs | |Class: org.apache.spark.sql.catalyst.expressions.Abs | |Usage: abs(expr) - Returns the absolute value of the numeric value.| +-------------------------------------------------------------------+
-- Describe a builtin scalar function. -- Returns function name, implementing class and usage and examples. DESC FUNCTION EXTENDED abs; +-------------------------------------------------------------------+ |function_desc | +-------------------------------------------------------------------+ |Function: abs | |Class: org.apache.spark.sql.catalyst.expressions.Abs | |Usage: abs(expr) - Returns the absolute value of the numeric value.| |Extended Usage: | | Examples: | | > SELECT abs(-1); | | 1 | | | +-------------------------------------------------------------------+
-- Describe a builtin aggregate function
DESC FUNCTION max;
+--------------------------------------------------------------+
|function_desc |
+--------------------------------------------------------------+
|Function: max |
|Class: org.apache.spark.sql.catalyst.expressions.aggregate.Max|
|Usage: max(expr) - Returns the maximum value of expr. |
+--------------------------------------------------------------+
-- Describe a builtin user defined aggregate function
-- Returns function name, implementing class and usage and examples.
DESC FUNCTION EXTENDED explode
+---------------------------------------------------------------+
|function_desc |
+---------------------------------------------------------------+
|Function: explode |
|Class: org.apache.spark.sql.catalyst.expressions.Explode |
|Usage: explode(expr) - Separates the elements of array expr |
| into multiple rows, or the elements of map expr into |
| multiple rows and columns. Unless specified otherwise, uses |
| the default column name col for elements of the array or |
| key and value for the elements of the map. |
|Extended Usage: |
| Examples: |
| > SELECT explode(array(10, 20)); |
| 10 |
| 20 |
+---------------------------------------------------------------+
{% endhighlight %}