a75dc80a76
### What changes were proposed in this pull request? Remove the unneeded embedded inline HTML markup by using the basic markdown syntax. Please see #28414 ### Why are the changes needed? Make the doc cleaner and easily editable by MD editors. ### Does this PR introduce _any_ user-facing change? No ### How was this patch tested? Manually build and check Closes #28451 from huaxingao/html_cleanup. Authored-by: Huaxin Gao <huaxing@us.ibm.com> Signed-off-by: Sean Owen <srowen@gmail.com>
111 lines
3.4 KiB
Markdown
111 lines
3.4 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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```sql
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{ DESC | DESCRIBE } [ QUERY ] input_statement
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```
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### Parameters
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* **QUERY**
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This clause is optional and may be omitted.
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* **input_statement**
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Specifies a result set producing statement and may be one of the following:
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* a `SELECT` statement
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* a `CTE(Common table expression)` statement
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* an `INLINE TABLE` statement
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* a `TABLE` statement
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* a `FROM` statement`
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Please refer to [select-statement](sql-ref-syntax-qry-select.html)
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for a detailed syntax of the query parameter.
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### Examples
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```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 an 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| Agecolumn|
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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| Agecolumn|
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+--------+---------+----------+
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```
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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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