title: PySpark createExternalTable() from SQLContext
body: <p>Using Spark 1.6.1. I have a bunch of tables in a mariaDb that I wish to convert to pySpark DataFrame objects. But createExternalTable() is throwing. For example:</p>
  
  <pre><code>In [292]: tn = sql.tableNames()[10]
  
  In [293]: df = sql.createExternalTable(tn)
  
  
  /home/charles/spark-1.6.1/python/lib/py4j-0.9-src.zip/py4j/protocol.py in get_return_value(answer, gateway_client, target_id, name)
  
  
  306                 raise Py4JJavaError(
  307                     "An error occurred while calling {0}{1}{2}.\n".
  --&gt; 308                     format(target_id, ".", name), value)
  309             else:
  310                 raise Py4JError(
  
  Py4JJavaError: An error occurred while calling o18.createExternalTable.
  : java.lang.RuntimeException: Tables created with SQLContext must be TEMPORARY. Use a HiveContext instead.
  at scala.sys.package$.error(package.scala:27)
  at org.apache.spark.sql.execution.SparkStrategies$DDLStrategy$.apply(SparkStrategies.scala:379)
  at org.apache.spark.sql.catalyst.planning.QueryPlanner$$anonfun$1.apply(QueryPlanner.scala:58)
  at org.apache.spark.sql.catalyst.planning.QueryPlanner$$anonfun$1.apply(QueryPlanner.scala:58)
  at scala.collection.Iterator$$anon$13.hasNext(Iterator.scala:371)
  at org.apache.spark.sql.catalyst.planning.QueryPlanner.plan(QueryPlanner.scala:59)
  at org.apache.spark.sql.execution.QueryExecution.sparkPlan$lzycompute(QueryExecution.scala:47)
  at org.apache.spark.sql.execution.QueryExecution.sparkPlan(QueryExecution.scala:45)
  at org.apache.spark.sql.execution.QueryExecution.executedPlan$lzycompute(QueryExecution.scala:52)
  at org.apache.spark.sql.execution.QueryExecution.executedPlan(QueryExecution.scala:52)
  at org.apache.spark.sql.execution.QueryExecution.toRdd$lzycompute(QueryExecution.scala:55)
  at org.apache.spark.sql.execution.QueryExecution.toRdd(QueryExecution.scala:55)
  at org.apache.spark.sql.SQLContext.createExternalTable(SQLContext.scala:695)
  at org.apache.spark.sql.SQLContext.createExternalTable(SQLContext.scala:668)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:606)
  at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
  at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:381)
  at py4j.Gateway.invoke(Gateway.java:259)
  at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
  at py4j.commands.CallCommand.execute(CallCommand.java:79)
  at py4j.GatewayConnection.run(GatewayConnection.java:209)
  at java.lang.Thread.run(Thread.java:745)
  </code></pre>
  
  <p>Same thing happens if I specify source='jdbc'. </p>
  
  <p>The table exists:</p>
  
  <pre><code>In [297]: sql.sql("SELECT * from {} LIMIT 5".format(tn)).show()
  +--------------------+-----+-----+-----+----+------+------+------+----------------------+----+----+----+-----+
  |                Date| Open| High|  Low|Last|Change|Settle|Volume|Prev_Day_Open_Interest|prod|exch|year|month|
  +--------------------+-----+-----+-----+----+------+------+------+----------------------+----+----+----+-----+
  |1999-10-29 00:00:...|245.0|245.0|245.0|null|  null| 245.0|   1.0|                   1.0|   C| CME|2001|    H|
  |1999-11-01 00:00:...|245.0|245.0|245.0|null|  null| 245.0|   0.0|                   1.0|   C| CME|2001|    H|
  |1999-11-02 00:00:...|245.0|245.0|245.0|null|  null| 245.0|   0.0|                   1.0|   C| CME|2001|    H|
  |1999-11-03 00:00:...|245.0|245.5|245.0|null|  null| 245.5|   5.0|                   6.0|   C| CME|2001|    H|
  |1999-11-04 00:00:...|245.5|245.5|245.5|null|  null| 245.5|   0.0|                   6.0|   C| CME|2001|    H|
  +--------------------+-----+-----+-----+----+------+------+------+----------------------+----+----+----+-----+
  </code></pre>
  
  <p>According to the error, this should work for HIVE data. I'm not using a HIVEContext, but an SQLContext. According to <a href="https://spark.apache.org/docs/latest/api/python/pyspark.sql.html" rel="nofollow">https://spark.apache.org/docs/latest/api/python/pyspark.sql.html</a> this is supported for ver >= 1.3. </p>
  
  <p>Is there a way to extract a DataFrame from a SqlTable?</p>