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https://issues.apache.org/jira/browse/CALCITE-5248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17585575#comment-17585575
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Jay Narale commented on CALCITE-5248:
-------------------------------------
[~julianhyde] These were the 2 major edge cases that I could think of. I will
also look out for other ones
> Support Column Aliasing feature in the where clause
> ---------------------------------------------------
>
> Key: CALCITE-5248
> URL: https://issues.apache.org/jira/browse/CALCITE-5248
> Project: Calcite
> Issue Type: New Feature
> Reporter: Jay Narale
> Priority: Major
>
> Based on the discussion here [1].
> The goal is to support column aliasing. An example is Teradata [2]
>
> A few edge cases to be considered for proper semantics
> 1. When SubQuery( maybe table) in from and Alias have the same name
> eg
> {code:java}
> SELECT c_customerId as c FROM ( SELECT c FROM table) WHERE c = 'test' {code}
> {code:java}
> SELECT trim(c_customer_name) as c FROM ( SELECT c FROM table) WHERE c =
> 'test' {code}
> Comments
> In a database, the execution order is *FROM > WHERE > SELECT* so the
> semantics should be that column in the subquery is given priority and a
> filter is applied to that column
> Behavior in Teradata
> Consistent with the above, a Filter is applied to the SubQuery
> 2. When a correlated column outside the query has the same name as the alias
> TBD
> Here I think the behavior should be identical to the behavior in OrderBy
>
> [1] - [https://lists.apache.org/thread/7zk5wqgsk64903w5mbt72pwjmsftx0kz]
> [2] -
> [https://docs.teradata.com/r/Teradata-Database-SQL-Fundamentals/June-2017/Basic-SQL-Syntax/Referencing-Object-Names-in-a-Request/Using-a-Column-Alias]
>
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