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https://issues.apache.org/jira/browse/HIVE-178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13799125#comment-13799125
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Ken Williams commented on HIVE-178:
-----------------------------------
Following up on [~electrum]'s {{dual}} approach - since the {{VALUES(...)}}
syntax isn't yet supported in Hive, one can do something like this:
{code}
CREATE TABLE dual (dummy STRING);
INSERT INTO TABLE dual SELECT count(*) FROM dual;
{code}
Then {{SELECT ... FROM dual;}} queries work as expected.
> SELECT without FROM should assume a one-row table with no columns.
> ------------------------------------------------------------------
>
> Key: HIVE-178
> URL: https://issues.apache.org/jira/browse/HIVE-178
> Project: Hive
> Issue Type: Wish
> Components: Query Processor, Testing Infrastructure
> Reporter: Adam Kramer
> Priority: Minor
> Labels: SQL
>
> SELECT 1+1;
> should just return '2', but instead hive fails because no table is listed.
> SELECT 1+1 FROM (empty table);
> should also just return '2', but instead hive "succeeds" because there is "no
> possible output," so it produces no output.
> So, currently we have to run
> SELECT 1+1 FROM (silly one-row dummy table);
> ...which runs a whole mapreduce step to ignore a column of data that is
> useless anyway. This is much easier due to local mode, but still, it would be
> nice to be able to SELECT without specifying a table and to get one row of
> output in moments instead of waiting for even a local-mode job to launch,
> complete, and return.
> This is especially useful for testing UDFs.
> Relatedly, an optimization by which Hive can tell that data from a table
> isn't even USED would be useful, because it means that the data needn't be
> queried...the only relevant info from the table would be the number of rows
> it has, which is available for free from the metastore.
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