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>
3.5 KiB
3.5 KiB
| layout | title | displayTitle | license |
|---|---|---|---|
| global | CREATE VIEW | CREATE VIEW | 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
Views are based on the result-set of an SQL query. CREATE VIEW constructs
a virtual table that has no physical data therefore other operations like
ALTER VIEW and DROP VIEW only change metadata.
Syntax
{% highlight sql %} CREATE [ OR REPLACE ] [ [ GLOBAL ] TEMPORARY ] VIEW [ IF NOT EXISTS ] view_identifier create_view_clauses AS query {% endhighlight %}
Parameters
OR REPLACE- If a view of same name already exists, it will be replaced.
[ GLOBAL ] TEMPORARY- TEMPORARY views are session-scoped and will be dropped when session ends because it skips persisting the definition in the underlying metastore, if any. GLOBAL TEMPORARY views are tied to a system preserved temporary database `global_temp`.
IF NOT EXISTS- Creates a view if it does not exists.
view_identifier-
Specifies a view name, which may be optionally qualified with a database name.
Syntax:[ database_name. ] view_name
create_view_clauses- These clauses are optional and order insensitive. It can be of following formats.
[ ( column_name [ COMMENT column_comment ], ... ) ]to specify column-level comments.[ COMMENT view_comment ]to specify view-level comments.[ TBLPROPERTIES ( property_name = property_value, ... ) ]to add metadata key-value pairs.
query- A SELECT statement that constructs the view from base tables or other views.
Examples
{% highlight sql %}
-- Create or replace view for experienced_employee with comments.
CREATE OR REPLACE VIEW experienced_employee
(ID COMMENT 'Unique identification number', Name)
COMMENT 'View for experienced employees'
AS SELECT id, name FROM all_employee
WHERE working_years > 5;
-- Create a global temporary view subscribed_movies if it does not exist.
CREATE GLOBAL TEMPORARY VIEW IF NOT EXISTS subscribed_movies
AS SELECT mo.member_id, mb.full_name, mo.movie_title
FROM movies AS mo INNER JOIN members AS mb
ON mo.member_id = mb.id;
{% endhighlight %}