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https://issues.apache.org/jira/browse/SPARK-20545?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997845#comment-15997845
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Xiao Li commented on SPARK-20545:
---------------------------------
Please reopen it if you still hit this issue. Thanks!
> union set operator should default to DISTINCT and not ALL semantics
> -------------------------------------------------------------------
>
> Key: SPARK-20545
> URL: https://issues.apache.org/jira/browse/SPARK-20545
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: N Campbell
>
> A set operation (i.e union) over two queries that produce identical row
> values should return the distinct set of rows and not all rows.
> ISO-SQL set operation semantics default to DISTINCT
> SPARK implementation is defaulting to ALL
> While SPARK allows DISTINCT keyword and some might assume ALL is faster, the
> wrong result set semantically is produced per standard (and commercial SQL
> systems including: ORACLE, DB2, Teradata, SQL Server etc.)
> select tsint.csint from cert.tsint
> union
> select tint.cint from cert.tint
> csint
> <null>
> -1
> 0
> 1
> 10
> <null>
> -1
> 0
> 1
> 10
> vs
> select tsint.csint from cert.tsint union distinct select tint.cint from
> cert.tint
> csint
> -1
> <null>
> 1
> 10
> 0
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