title: How to partition a table by month and day in hive
body: <p>I have created a table with:</p>
  
  <pre><code>CREATE EXTERNAL TABLE extab (
  vendorID string, 
  orderID string , 
  ordertime string
  ) 
  location '/common_folder/data'
  </code></pre>
  
  <p>Then I created a partition by month and day</p>
  
  <pre><code>CREATE EXTERNAL TABLE part_extab(
  endorID string, 
  orderID string , 
  ordertime string
  ) 
  PARTITIONED by (month string, day string)
  location '/common_folder/data'
  </code></pre>
  
  <p>Then insert data into the partitioned table</p>
  
  <pre><code>INSERT OVERWRITE TABLE 
  select vendorId, orderId, ordertime , month, day
  FROM extab
  </code></pre>
  
  <p>HOW do I extract month , day from ordertime ??</p>