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[SPARK-28810][DOC][SQL] Document SHOW TABLES in SQL Reference

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### 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>
This commit is contained in:
shivusondur 2019-10-12 09:21:44 -05:00 committed by Sean Owen
parent 81362956a7
commit aa1acfe078
1 changed files with 86 additions and 1 deletions
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docs/sql-ref-syntax-aux-show-tables.md
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@ -18,5 +18,90 @@ license: |
See the License for the specific language governing permissions and See the License for the specific language governing permissions and
limitations under the License. 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)