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Xiao Li resolved SPARK-20841. ----------------------------- Resolution: Fixed Fix Version/s: 2.3.0 > 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 (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org