## What changes were proposed in this pull request?
The current implementation of "CREATE TEMPORARY TABLE USING datasource..." is NOT creating any intermediate temporary data directory like temporary HDFS folder, instead, it only stores a SQL string in memory. Probably we should use "TEMPORARY VIEW" instead.
This PR assumes a temporary table has to link with some temporary intermediate data. It follows the definition of temporary table like this (from [hortonworks doc](https://docs.hortonworks.com/HDPDocuments/HDP2/HDP-2.3.0/bk_dataintegration/content/temp-tables.html)):
> A temporary table is a convenient way for an application to automatically manage intermediate data generated during a complex query
**Example**:
```
scala> spark.sql("CREATE temporary view my_tab7 (c1: String, c2: String) USING org.apache.spark.sql.execution.datasources.csv.CSVFileFormat OPTIONS (PATH '/Users/seanzhong/csv/cars.csv')")
scala> spark.sql("select c1, c2 from my_tab7").show()
+----+-----+
| c1| c2|
+----+-----+
|year| make|
|2012|Tesla|
...
```
It NOW prints a **deprecation warning** if "CREATE TEMPORARY TABLE USING..." is used.
```
scala> spark.sql("CREATE temporary table my_tab7 (c1: String, c2: String) USING org.apache.spark.sql.execution.datasources.csv.CSVFileFormat OPTIONS (PATH '/Users/seanzhong/csv/cars.csv')")
16/05/31 10:39:27 WARN SparkStrategies$DDLStrategy: CREATE TEMPORARY TABLE tableName USING... is deprecated, please use CREATE TEMPORARY VIEW viewName USING... instead
```
## How was this patch tested?
Unit test.
Author: Sean Zhong <seanzhong@databricks.com>
Closes#13414 from clockfly/create_temp_view_using.
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