From aa1acfe078ac7eee4602d178c46277c200f6d629 Mon Sep 17 00:00:00 2001
From: shivusondur <shivusondur@gmail.com>
Date: Sat, 12 Oct 2019 09:21:44 -0500
Subject: [PATCH] [SPARK-28810][DOC][SQL] Document SHOW TABLES in SQL Reference

### What changes were proposed in this pull request?
Added the reference for SHOW TABLES sql command.

### Why are the changes needed?
To help the customer usage

### Does this PR introduce any user-facing change?
It updates the Sql command reference doc.

### How was this patch tested?
<details>
<summary> Attached the Snap</summary>

![image](https://user-images.githubusercontent.com/7912929/66623173-1eac1b80-ec08-11e9-8357-9f6323e5fc48.png)

![image](https://user-images.githubusercontent.com/7912929/65384657-87f3e980-dd42-11e9-90fa-6650ee68e005.png)

</details>

Closes #25561 from shivusondur/jiraSHOWTBLS.

Authored-by: shivusondur <shivusondur@gmail.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>
---
 docs/sql-ref-syntax-aux-show-tables.md | 87 +++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 1 deletion(-)

diff --git a/docs/sql-ref-syntax-aux-show-tables.md b/docs/sql-ref-syntax-aux-show-tables.md
index e4340d608b..46cfe40dc2 100644
--- a/docs/sql-ref-syntax-aux-show-tables.md
+++ b/docs/sql-ref-syntax-aux-show-tables.md
@@ -18,5 +18,90 @@ license: |
   See the License for the specific language governing permissions and
   limitations under the License.
 ---
+### Description
 
-**This page is under construction**
+The `SHOW TABLES` statement returns all the tables for an optionally specified database.
+Additionally, the output of this statement may be filtered by an optional matching
+pattern. If no database is specified then the tables are returned from the 
+current database.
+
+### Syntax
+{% highlight sql %}
+SHOW TABLES [{FROM|IN} database_name] [LIKE 'regex_pattern']
+{% endhighlight %}
+
+### Parameters
+<dl>
+  <dt><code><em>{FROM|IN} database_name</em></code></dt>
+  <dd>
+     Specifies the database name from which tables are listed.
+  </dd>
+  <dt><code><em>LIKE regex_pattern</em></code></dt>
+  <dd>
+     Specifies the regular expression pattern that is used to filter out unwanted tables. 
+     <ul> 
+          <li> Except for `*` and `|` character, the pattern works like a regex.</li>
+          <li> `*` alone matches 0 or more characters and `|` is used to separate multiple different regexes,
+           any of which can match. </li>
+          <li> The leading and trailing blanks are trimmed in the input pattern before processing.</li>
+     </ul>
+    
+  </dd>
+</dl>
+
+### Example
+{% highlight sql %}
+-- List all tables in default database
+SHOW TABLES;
+  +-----------+------------+--------------+--+
+  | database  | tableName  | isTemporary  |
+  +-----------+------------+--------------+--+
+  | default   | sam        | false        |
+  | default   | sam1       | false        |
+  | default   | suj        | false        |
+  +-----------+------------+--------------+--+
+
+-- List all tables from userdb database 
+SHOW TABLES FROM userdb;
+  +-----------+------------+--------------+--+
+  | database  | tableName  | isTemporary  |
+  +-----------+------------+--------------+--+
+  | userdb    | user1      | false        |
+  | userdb    | user2      | false        |
+  +-----------+------------+--------------+--+
+
+-- List all tables in userdb database
+SHOW TABLES IN userdb;
+  +-----------+------------+--------------+--+
+  | database  | tableName  | isTemporary  |
+  +-----------+------------+--------------+--+
+  | userdb    | user1      | false        |
+  | userdb    | user2      | false        |
+  +-----------+------------+--------------+--+
+
+-- List all tables from default database matching the pattern `sam*`
+SHOW TABLES FROM default LIKE 'sam*';
+  +-----------+------------+--------------+--+
+  | database  | tableName  | isTemporary  |
+  +-----------+------------+--------------+--+
+  | default   | sam        | false        |
+  | default   | sam1       | false        |
+  +-----------+------------+--------------+--+
+  
+-- List all tables matching the pattern `sam*|suj`
+SHOW TABLES  LIKE 'sam*|suj';
+  +-----------+------------+--------------+--+
+  | database  | tableName  | isTemporary  |
+  +-----------+------------+--------------+--+
+  | default   | sam        | false        |
+  | default   | sam1       | false        |
+  | default   | suj        | false        |
+  +-----------+------------+--------------+--+
+
+{% endhighlight %}
+
+### Related statements
+- [CREATE TABLE](sql-ref-syntax-ddl-create-table.html)
+- [DROP TABLE](sql-ref-syntax-ddl-drop-table.html)
+- [CREATE DATABASE](sql-ref-syntax-ddl-create-database.html)
+- [DROP DATABASE](sql-ref-syntax-ddl-drop-database.html)
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