babefdee1c
### What changes were proposed in this pull request? Standardize sql reference ### Why are the changes needed? To have consistent docs ### Does this PR introduce any user-facing change? Yes ### How was this patch tested? Tested using jykyll build --serve Closes #26721 from huaxingao/spark-30085. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Sean Owen <sean.owen@databricks.com>
108 lines
3.8 KiB
Markdown
108 lines
3.8 KiB
Markdown
---
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layout: global
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title: DESCRIBE QUERY
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displayTitle: DESCRIBE QUERY
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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 `DESCRIBE QUERY` statement is used to return the metadata of output
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of a query. A shorthand `DESC` may be used instead of `DESCRIBE` to
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describe the query output.
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### Syntax
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{% highlight sql %}
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{ DESC | DESCRIBE } [ QUERY ] input_statement
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{% endhighlight %}
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### Parameters
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<dl>
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<dt><code><em>QUERY</em></code></dt>
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<dd>This clause is optional and may be omitted.</dd>
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<dt><code><em>input_statement</em></code></dt>
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<dd>
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Specifies a result set producing statement and may be one of the following:
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<ul>
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<li>a <code>SELECT</code> statement</li>
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<li>a <code>CTE(Common table expression)</code> statement</li>
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<li>an <code>INLINE TABLE</code> statement</li>
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<li>a <code>TABLE</code> statement</li>
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<li>a <code>FROM</code> statement</li>
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</ul>
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Please refer to <a href="sql-ref-syntax-qry-select.html">select-statement</a>
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for a detailed syntax of the query parameter.
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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`
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CREATE TABLE person (name STRING , age INT COMMENT 'Age column', address STRING);
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-- Returns column metadata information for a simple select query
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DESCRIBE QUERY select age, sum(age) FROM person GROUP BY age;
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+--------+---------+----------+
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|col_name|data_type|comment |
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+--------+---------+----------+
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|age |int |Age column|
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|sum(age)|bigint |null |
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+--------+---------+----------+
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-- Returns column metadata information for common table expression (`CTE`).
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DESCRIBE QUERY WITH all_names_cte
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AS (SELECT name from person) SELECT * FROM all_names_cte;
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+--------+---------+-------+
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|col_name|data_type|comment|
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+--------+---------+-------+
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|name |string |null |
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+--------+---------+-------+
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-- Returns column metadata information for a inline table.
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DESC QUERY VALUES(100, 'John', 10000.20D) AS employee(id, name, salary);
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+--------+---------+-------+
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|col_name|data_type|comment|
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+--------+---------+-------+
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|id |int |null |
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|name |string |null |
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|salary |double |null |
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+--------+---------+-------+
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-- Returns column metadata information for `TABLE` statement.
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DESC QUERY TABLE person;
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+--------+---------+----------+
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|col_name|data_type|comment |
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+--------+---------+----------+
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|name |string |null |
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|age |int |Age column|
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|address |string |null |
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+--------+---------+----------+
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-- Returns column metadata information for a `FROM` statement.
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-- `QUERY` clause is optional and can be omitted.
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DESCRIBE FROM person SELECT age;
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+--------+---------+----------+
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|col_name|data_type|comment |
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+--------+---------+----------+
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|age |int |Age column|
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+--------+---------+----------+
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{% endhighlight %}
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### Related Statements
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- [DESCRIBE DATABASE](sql-ref-syntax-aux-describe-database.html)
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- [DESCRIBE TABLE](sql-ref-syntax-aux-describe-table.html)
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- [DESCRIBE FUNCTION](sql-ref-syntax-aux-describe-function.html)
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