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From "Sunitha Kambhampati (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-19602) Unable to query using the fully qualified column name of the form ( <DBNAME>.<TABLENAME>.<COLUMNNAME>)
Date Wed, 01 Aug 2018 18:43:00 GMT

    [ https://issues.apache.org/jira/browse/SPARK-19602?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16565802#comment-16565802
] 

Sunitha Kambhampati commented on SPARK-19602:
---------------------------------------------

The design doc is also uploaded [here|https://drive.google.com/file/d/1zKm3aNZ3DpsqIuoMvRsf0kkDkXsAasxH/view]

> Unable to query using the fully qualified column name of the form ( <DBNAME>.<TABLENAME>.<COLUMNNAME>)
> ------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-19602
>                 URL: https://issues.apache.org/jira/browse/SPARK-19602
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 2.1.0
>            Reporter: Sunitha Kambhampati
>            Assignee: Sunitha Kambhampati
>            Priority: Major
>         Attachments: Design_ColResolution_JIRA19602.pdf
>
>
> 1) Spark SQL fails to analyze this query:  select db1.t1.i1 from db1.t1, db2.t1
> Most of the other database systems support this ( e.g DB2, Oracle, MySQL).
> Note: In DB2, Oracle, the notion is of <schema>.<tablename>.<columnname>
> 2) Another scenario where this fully qualified name is useful is as follows:
>   // current database is db1. 
>   select t1.i1 from t1, db2.t1   
> If the i1 column exists in both tables: db1.t1 and db2.t1, this will throw an error during
column resolution in the analyzer, as it is ambiguous. 
> Lets say the user intended to retrieve i1 from db1.t1 but in the example db2.t1 only
has i1 column. The query would still succeed instead of throwing an error.  
> One way to avoid confusion would be to explicitly specify using the fully qualified name
db1.t1.i1 
> For e.g:  select db1.t1.i1 from t1, db2.t1  
> Workarounds:
> There is a workaround for these issues, which is to use an alias. 



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