[
https://issues.apache.org/jira/browse/SPARK-20841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Xiao Li reassigned SPARK-20841:
-------------------------------
Assignee: Takeshi Yamamuro
> Support table column aliases in FROM clause
> -------------------------------------------
>
> Key: SPARK-20841
> URL: https://issues.apache.org/jira/browse/SPARK-20841
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.0.0
> Reporter: Josh Rosen
> Assignee: Takeshi Yamamuro
> Priority: Minor
> Fix For: 2.3.0
>
>
> Some SQL dialects support a relatively obscure "table column aliases" feature
> where you can rename columns when aliasing a relation in a {{FROM}} clause.
> For example:
> {code}
> SELECT * FROM onecolumn AS a(x) JOIN onecolumn AS b(y) ON a.x = b.y
> {code}
> Spark does not currently support this. I would like to add support for this
> in order to allow me to run a corpus of existing queries which depend on this
> syntax.
> There's a good writeup on this at
> http://modern-sql.com/feature/table-column-aliases, which has additional
> examples and describes other databases' degrees of support for this feature.
> One tricky thing to figure out will be whether FROM clause column aliases
> take precedence over aliases in the SELECT clause. When adding support for
> this, we should make sure to add sufficient testing of several corner-cases,
> including:
> * Aliasing in both the SELECT and FROM clause
> * Aliasing columns in the FROM clause both with and without an explicit AS.
> * Aliasing the wrong number of columns in the FROM clause, both greater and
> fewer columns than were selected in the SELECT clause.
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org
For additional commands, e-mail: issues-h...@spark.apache.org
