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https://issues.apache.org/jira/browse/CALCITE-4305?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde resolved CALCITE-4305.
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Fix Version/s: 1.27.0
Resolution: Fixed
Fixed in
[c2527cc|https://github.com/apache/calcite/commit/c2527ccf440f7750bfbabd2063c402440c5b32a0].
> Implicit column alias for single-column VALUES, and UNNEST of ARRAY and
> MULTISET constructors
> ---------------------------------------------------------------------------------------------
>
> Key: CALCITE-4305
> URL: https://issues.apache.org/jira/browse/CALCITE-4305
> Project: Calcite
> Issue Type: Bug
> Reporter: Julian Hyde
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.27.0
>
>
> Single-column UNNEST with a single alias should assign that alias to both a
> table and the unique column. For example, PostgreSQL returns a column called
> 'unnest' in the first, and 'fruit' in all of the rest:
> {code}
> select * from UNNEST(array ['apple', 'banana', 'pear']);
> select * from UNNEST(array ['apple', 'banana', 'pear']) as fruit;
> select * from UNNEST(array ['apple', 'banana', 'pear']) as t(fruit);
> select t.* from UNNEST(array ['apple', 'banana', 'pear']) as t(fruit);
> select fruit.* from UNNEST(array ['apple', 'banana', 'pear']) as fruit;
> {code}
> Thus {{FROM UNNEST(...) AS x}} is creating a table alias {{x}} and a column
> alias {{x}}.
> This only happens for UNNEST. When aliasing other single-column relations the
> column name is retained, such as a SELECT-FROM-UNNEST sub-query as follows:
> {code}
> SELECT fruit.*
> FROM (SELECT * FROM UNNEST(array ['apple', 'banana', 'pear']) as x) as fruit;
> x
> ======
> apple
> banana
> pear
> {code}
> BigQuery has [similar
> behavior|https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#any_value].
> As an extension to PostgreSQL and BigQuery, we also derive a column alias for
> UNNEST of single-column MULTISET and single-column VALUES. Examples:
> {code}
> SELECT f FROM UNNEST(MULTISET ['apple', 'banana', 'pear']) AS f;
> SELECT f FROM (VALUES 'apple', 'banana', 'pear') AS f;
> {code}
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