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>
131 lines
3.6 KiB
Markdown
131 lines
3.6 KiB
Markdown
---
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layout: global
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title: SELECT
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displayTitle: WHERE clause
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license: |
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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---
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### Description
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The <code>WHERE</code> clause is used to limit the results of the <code>FROM</code>
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clause of a query or a subquery based on the specified condition.
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### Syntax
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{% highlight sql %}
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WHERE boolean_expression
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{% endhighlight %}
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### Parameters
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<dl>
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<dt><code><em>boolean_expression</em></code></dt>
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<dd>
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Specifies any expression that evaluates to a result type <code>boolean</code>. Two or
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more expressions may be combined together using the logical
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operators ( <code>AND</code>, <code>OR</code> ).
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</dd>
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</dl>
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### Examples
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{% highlight sql %}
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CREATE TABLE person (id INT, name STRING, age INT);
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INSERT INTO person VALUES
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(100, 'John', 30),
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(200, 'Mary', NULL),
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(300, 'Mike', 80),
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(400, 'Dan', 50);
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-- Comparison operator in `WHERE` clause.
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SELECT * FROM person WHERE id > 200 ORDER BY id;
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+---+----+---+
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| id|name|age|
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+---+----+---+
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|300|Mike| 80|
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|400| Dan| 50|
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+---+----+---+
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-- Comparison and logical operators in `WHERE` clause.
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SELECT * FROM person WHERE id = 200 OR id = 300 ORDER BY id;
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+---+----+----+
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| id|name| age|
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+---+----+----+
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|200|Mary|null|
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|300|Mike| 80|
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+---+----+----+
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-- IS NULL expression in `WHERE` clause.
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SELECT * FROM person WHERE id > 300 OR age IS NULL ORDER BY id;
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+---+----+----+
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| id|name| age|
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+---+----+----+
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|200|Mary|null|
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|400| Dan| 50|
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+---+----+----+
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-- Function expression in `WHERE` clause.
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SELECT * FROM person WHERE length(name) > 3 ORDER BY id;
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+---+----+----+
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| id|name| age|
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+---+----+----+
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|100|John| 30|
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|200|Mary|null|
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|300|Mike| 80|
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+---+----+----+
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-- `BETWEEN` expression in `WHERE` clause.
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SELECT * FROM person WHERE id BETWEEN 200 AND 300 ORDER BY id;
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+---+----+----+
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| id|name| age|
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+---+----+----+
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|200|Mary|null|
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|300|Mike| 80|
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+---+----+----+
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-- Scalar Subquery in `WHERE` clause.
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SELECT * FROM person WHERE age > (SELECT avg(age) FROM person);
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+---+----+---+
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| id|name|age|
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+---+----+---+
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|300|Mike| 80|
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+---+----+---+
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-- Correlated Subquery in `WHERE` clause.
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SELECT * FROM person AS parent
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WHERE EXISTS (
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SELECT 1 FROM person AS child
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WHERE parent.id = child.id AND child.age IS NULL
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);
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+---+----+----+
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|id |name|age |
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+---+----+----+
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|200|Mary|null|
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+---+----+----+
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{% endhighlight %}
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### Related Statements
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* [SELECT Main](sql-ref-syntax-qry-select.html)
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* [GROUP BY Clause](sql-ref-syntax-qry-select-groupby.html)
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* [HAVING Clause](sql-ref-syntax-qry-select-having.html)
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* [ORDER BY Clause](sql-ref-syntax-qry-select-orderby.html)
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* [SORT BY Clause](sql-ref-syntax-qry-select-sortby.html)
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* [CLUSTER BY Clause](sql-ref-syntax-qry-select-clusterby.html)
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* [DISTRIBUTE BY Clause](sql-ref-syntax-qry-select-distribute-by.html)
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* [LIMIT Clause](sql-ref-syntax-qry-select-limit.html)
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