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https://issues.apache.org/jira/browse/HIVE-4697?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13679883#comment-13679883
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Brock Noland commented on HIVE-4697:
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FWIW, I don't care what JIRA we take this issue forward with but let's link to
any related issues and resolve any duplicates.
> Subqueries with IN and NOT IN
> -----------------------------
>
> Key: HIVE-4697
> URL: https://issues.apache.org/jira/browse/HIVE-4697
> Project: Hive
> Issue Type: New Feature
> Components: Query Processor
> Reporter: Matthew Weaver
> Assignee: Matthew Weaver
> Original Estimate: 840h
> Remaining Estimate: 840h
>
> h5. Functional Requirements
> * Support {{WHERE x IN (<column subquery>);}}
> ** {{<column subquery>}} returns one column, any number of rows.
> * Support {{WHERE x NOT IN (<column subquery>)}};
> * Support same types of subqueries in {{HAVING}}.
> ** E.g.
> {code:sql}
> SELECT key FROM t1 GROUP BY key
> HAVING COUNT(value) IN (SELECT p FROM t2); {code}
> * Correlated subqueries not supported, for now at least
> ** But still need to check for correlation, and bail if it occurs.
> ** Correlated subquery:
> *** A subquery that references a table that appears in a containing query
> ([MySQL|http://dev.mysql.com/doc/refman/5.7/en/correlated-subqueries.html]),
> thus requiring subquery evaluation to look outside its scope.
> *** The subquery depends on the outer query for its values, so the subquery
> must be executed once for each row of the outer query. Also known as
> _repeating Subqueries_.
> h5. Tasks
> * Rewrite {{IN (<column-subquery>)}} as a {{LEFT SEMI JOIN}}.
> ** Not ready for public consumption. In particular, no check for correlated
> terms.
> ** With test queries.
> * Add check for correlated terms, return informative error message.
> * Rewrite {{WHERE NOT IN (<column-subquery>)}} as a {{LEFT OUTER JOIN}}.
> ** Return rows that don't match the right side
> * Rewrite subqueries in {{HAVING}}, using {{LEFT SEMI JOIN}} and {{LEFT OUTER
> JOIN}} as above.
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