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>
4 KiB
| layout | title | displayTitle | license |
|---|---|---|---|
| global | DESCRIBE DATABASE | DESCRIBE DATABASE | 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 DATABASE statement returns the metadata of an existing database. The metadata information includes database
name, database comment, and database location on the filesystem. If the optional EXTENDED option is specified, it
returns the basic metadata information along with the database properties. The DATABASE and SCHEMA are
interchangeable.
Syntax
{% highlight sql %} { DESC | DESCRIBE } DATABASE [ EXTENDED ] db_name {% endhighlight %}
Parameters
db_name- Specifies a name of an existing database or an existing schema in the system. If the name does not exist, an exception is thrown.
Example
{% highlight sql %} -- Create employees DATABASE CREATE DATABASE employees COMMENT 'For software companies';
-- Describe employees DATABASE. -- Returns Database Name, Description and Root location of the filesystem -- for the employees DATABASE. DESCRIBE DATABASE employees; +-------------------------+-----------------------------+ |database_description_item| database_description_value| +-------------------------+-----------------------------+ | Database Name| employees| | Description| For software companies| | Location|file:/Users/Temp/employees.db| +-------------------------+-----------------------------+
-- Create employees DATABASE CREATE DATABASE employees COMMENT 'For software companies';
-- Alter employees database to set DBPROPERTIES ALTER DATABASE employees SET DBPROPERTIES ('Create-by' = 'Kevin', 'Create-date' = '09/01/2019');
-- Describe employees DATABASE with EXTENDED option to return additional database properties DESCRIBE DATABASE EXTENDED employees; +-------------------------+---------------------------------------------+ |database_description_item| database_description_value| +-------------------------+---------------------------------------------+ | Database Name| employees| | Description| For software companies| | Location| file:/Users/Temp/employees.db| | Properties|((Create-by,kevin), (Create-date,09/01/2019))| +-------------------------+---------------------------------------------+
-- Create deployment SCHEMA CREATE SCHEMA deployment COMMENT 'Deployment environment';
-- Describe deployment, the DATABASE and SCHEMA are interchangeable, their meaning are the same. DESC DATABASE deployment; +-------------------------+------------------------------+ |database_description_item|database_description_value | +-------------------------+------------------------------+ | Database Name| deployment| | Description| Deployment environment| | Location|file:/Users/Temp/deployment.db| +-------------------------+------------------------------+ {% endhighlight %}