Hi Shirley, I think this query would give you an error currently, for two reasons:
1. The select list does not contain the group by column and distinct track group by user is indeterminate - what value of track do you want to report here on the group of users? 2. We do not have order by yet though you can sort of simulate it with a sort by clause and 1 reducer. Can you explain more in terms of what you want the SQL to achieve? Also the hive wiki contains a number of presentations that describe how SQL gets converted to Map/Reduce plans at a high level. Check them out at http://wiki.apache.org/hadoop/Hive/Presentations Ashish ________________________________ From: Jeff Hammerbacher [mailto:[email protected]] Sent: Saturday, December 20, 2008 11:35 AM To: [email protected] Subject: Re: question about mapred translation Hey Shirley, Welcome to Hive! Once you've gotten Hive up and running and have created the "music" table, you should be able to say "EXPLAIN <query>", where <query> is the query specified below (or any other query). For more detailed information, you can say "EXPLAIN EXTENDED <query>". The output from the EXPLAIN might be a little obtuse, so if you still have questions, I'm sure more knowledgeable Hive folks can give you insight into the planner. Regards, Jeff On Sat, Dec 20, 2008 at 11:48 AM, Shirley Cohen <[email protected]<mailto:[email protected]>> wrote: Hi, I'm just getting started with Hive. I was wondering if anyone can tell me how Hive would translate the following SQL query into MapReduce: select distinct track, count(track) from music where date_listened between '12-10-2008' and '12-11-2008' group by user order by count(track) desc How many mapred jobs would it use? How would the map and red functions looks like? Also, does Hive have a utility that gives you this information? Thanks, Shirley
