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Hive >> mail # user >> UNION ALL - what is the simplest form


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Re: UNION ALL - what is the simplest form
Hi Anand

You necessarily don't need to go in for UNION ALL for your requirement.

Use INSERT INTO instead, which has less overhead. It is supported from hive 0.8 .

INSERT INTO main_table SELECT * FROM stage_table;

Or an even better approach if you are just copying whole data from one table to another would be to use a hdfs copy/move.

LOAD DATA INPATH 'location/of/stage_table' INTO TABLE 'main_table';

Regards
Bejoy KS

Sent from handheld, please excuse typos.

-----Original Message-----
From: "Balaraman, Anand" <[EMAIL PROTECTED]>
Date: Thu, 16 Aug 2012 11:36:49
To: <[EMAIL PROTECTED]>
Reply-To: [EMAIL PROTECTED]
Subject: UNION ALL - what is the simplest form

Hi

 

I am trying to consolidate one of my staged tables with a primary table
(incremental loading).

Simply need to merge 2 tables using UNION ALL.

Tried the following:

 

        select * from main_table UNION ALL select * from stage_table

but, not able to execute it -> Error in semantic analysis: Top level
UNION is not supported currently; use a subquery for the UNION

 

But, HIVE language manual says:

UNION ALL is used to combine the result from multiple SELECT statements
into a single result set.

 

Syntax:

        select_statement UNION ALL select_statement UNION ALL
select_statement ...

 

Have I gone wrong with the syntax anywhere in my query ?

 

Regards

 

Anand B

 
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NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB