92ae271081
### What changes were proposed in this pull request? Document SHOW COLUMNS statement in SQL Reference Guide. ### Why are the changes needed? Currently Spark lacks documentation on the supported SQL constructs causing confusion among users who sometimes have to look at the code to understand the usage. This is aimed at addressing this issue. ### Does this PR introduce any user-facing change? Yes. **Before:** There was no documentation for this. **After.** <img width="1234" alt="Screen Shot 2019-09-02 at 11 07 48 PM" src="https://user-images.githubusercontent.com/14225158/64148033-0fe77300-cdd7-11e9-93ee-e5951c7ed33c.png"> <img width="1234" alt="Screen Shot 2019-09-02 at 11 08 08 PM" src="https://user-images.githubusercontent.com/14225158/64148039-137afa00-cdd7-11e9-8bec-634ea9d2594c.png"> <img width="1234" alt="Screen Shot 2019-09-02 at 11 11 45 PM" src="https://user-images.githubusercontent.com/14225158/64148046-17a71780-cdd7-11e9-91c3-95a9c97e7a77.png"> ### How was this patch tested? Tested using jykyll build --serve Closes #25531 from dilipbiswal/ref-doc-show-columns. Lead-authored-by: Dilip Biswal <dbiswal@us.ibm.com> Co-authored-by: Xiao Li <gatorsmile@gmail.com> Signed-off-by: Xiao Li <gatorsmile@gmail.com>
98 lines
2.8 KiB
Markdown
98 lines
2.8 KiB
Markdown
---
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layout: global
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title: SHOW COLUMNS
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displayTitle: SHOW COLUMNS
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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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Return the list of columns in a table. If the table does not exist, an exception is thrown.
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### Syntax
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{% highlight sql %}
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SHOW COLUMNS table [ database ]
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{% endhighlight %}
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### Parameters
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<dl>
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<dt><code><em>table</em></code></dt>
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<dd>
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Specifies the table name of an existing table. The table may be optionally qualified
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with a database name.<br><br>
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<b>Syntax:</b>
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<code>
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{ IN | FROM } [database_name.]table_name
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</code><br><br>
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<b>Note:</b>
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Keywords <code>IN</code> and <code>FROM</code> are interchangeable.
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</dd>
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<dt><code><em>database</em></code></dt>
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<dd>
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Specifies an optional database name. The table is resolved from this database when it
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is specified. Please note that when this parameter is specified then table
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name should not be qualified with a different database name. <br><br>
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<b>Syntax:</b>
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<code>
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{ IN | FROM } database_name
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</code><br><br>
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<b>Note:</b>
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Keywords <code>IN</code> and <code>FROM</code> are interchangeable.
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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 `customer` table in `salesdb` database;
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USE salesdb;
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CREATE TABLE customer(cust_cd INT,
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name VARCHAR(100),
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cust_addr STRING);
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-- List the columns of `customer` table in current database.
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SHOW COLUMNS IN customer;
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+---------+
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|col_name |
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+---------+
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|cust_cd |
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|name |
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|cust_addr|
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+---------+
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-- List the columns of `customer` table in `salesdb` database.
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SHOW COLUMNS IN salesdb.customer;
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+---------+
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|col_name |
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+---------+
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|cust_cd |
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|name |
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|cust_addr|
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+---------+
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-- List the columns of `customer` table in `salesdb` database
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SHOW COLUMNS IN customer IN salesdb;
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+---------+
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|col_name |
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+---------+
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|cust_cd |
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|name |
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|cust_addr|
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+---------+
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{% endhighlight %}
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### Related Statements
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- [DESCRIBE TABLE](sql-ref-syntax-aux-describe-table.html)
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- [SHOW TABLE](sql-ref-syntax-aux-show-table.html)
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