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From Keith Wiley <kwi...@keithwiley.com>
Subject Re: order by date
Date Tue, 13 Mar 2012 17:00:45 GMT
Is see, you store the date-time as a lexicographically sortable string.  That's fine, but I'm
operating on existing csv tables.  I guess I could whip up a hadoop job to convert all the
date-time columns to lexicographic strings and then wrap hive around the resulting converted
tables.  I was just wondering if there was a more direct approach, whether I could apply hive
to the original csv tables.

*Would* the date functions work in the way I suggested in my first post or do you think a
lexicographic conversion is practically required to perform date-ordering on query results?

On Mar 13, 2012, at 09:49 , Tucker, Matt wrote:

> Hi Keith,
> 
> We generally store date columns as a string in a similar format to ISO 8601 (yyyy-mm-dd
hh:MM:ss).  This way, when we put the date column in the ORDER BY clause, it will be sorted
chronologically.  It also saves us the trouble of whipping out a unix timestamp calculator
to figure out what we're looking at.
> 
> There is supposed to be a TIMESTAMP data type in Hive 0.8, but I haven't found any documentation
on it yet.
> 
> Matt Tucker
> 
> -----Original Message-----
> From: Keith Wiley [mailto:kwiley@keithwiley.com] 
> Sent: Tuesday, March 13, 2012 12:45 PM
> To: user@hive.apache.org
> Subject: order by date
> 
> I realize that hive doesn't have a date type for the columns and I realize that hive
*does* have various date functions.  I just haven't found a concrete example of how these
two issues are brought together.  Ordering the results of a sql query is done by adding "order
by dateColName" to the query.  Are the date functions supposed to be used in the form "order
by UNIX_TIMESTAMP(dateColName, 'yyyy-MM-dd')"?  Does the function just go right into the "order
by" clause like that or is that totally wrong?
> 
> How does one order query results by a date column?  Am I on the right track?
> 
> Thanks.


________________________________________________________________________________
Keith Wiley     kwiley@keithwiley.com     keithwiley.com    music.keithwiley.com

"Yet mark his perfect self-contentment, and hence learn his lesson, that to be
self-contented is to be vile and ignorant, and that to aspire is better than to
be blindly and impotently happy."
                                           --  Edwin A. Abbott, Flatland
________________________________________________________________________________


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