[SPARK-28822][DOC][SQL]Document USE DATABASE in SQL Reference.

docs/_data/menu-sql.yaml

@@ -139,6 +139,8 @@
                   url: sql-ref-syntax-qry-select-limit.html
                 - text: Set operations
                   url: sql-ref-syntax-qry-select-setops.html
+                - text: USE database
+                  url: sql-ref-syntax-qry-select-usedb.html
                 - text: Common Table Expression(CTE)
                   url: sql-ref-syntax-qry-select-cte.html
                 - text: Subqueries

docs/sql-ref-syntax-qry-select-usedb.md

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+---
+layout: global
+title: USE Database
+displayTitle: USE Database
+license: |
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+     http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+---
+
+### Description
+`USE` statement is used to set the current database. After the current database is set,
+the unqualified database artifacts such as tables, functions and views that are 
+referenced by SQLs are resolved from the current database. 
+The default database name is 'default'.
+
+### Syntax
+{% highlight sql %}
+USE database_name
+{% endhighlight %}
+
+### Parameter
+
+<dl>
+  <dt><code><em>database_name</em></code></dt>
+  <dd>
+     Name of the database will be used. If the database does not exist, an exception will be thrown.
+  </dd>
+</dl>
+
+### Example
+{% highlight sql %}
+-- Use the 'userdb' which exists.
+USE userdb;
++---------+--+
+| Result  |
++---------+--+
++---------+--+
+
+-- Use the 'userdb1' which doesn't exist
+USE userdb1;
+Error: org.apache.spark.sql.catalyst.analysis.NoSuchDatabaseException: Database 'userdb1' not found;(state=,code=0)
+{% endhighlight %}
+
+### Related statements.
+- [CREATE DATABASE](sql-ref-syntax-ddl-create-database.html)
+- [DROP DATABASE](sql-ref-syntax-ddl-drop-database.html)
+- [CREATE TABLE ](sql-ref-syntax-ddl-create-table.html)
+