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https://issues.apache.org/jira/browse/CALCITE-6508?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17873651#comment-17873651
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Julian Hyde commented on CALCITE-6508:
--------------------------------------
{quote}you wouldn't happen to remember why subqueries were excluded?
{quote}
Subqueries introduce problems with commas. E.g.
{code:java}
ARRAY [
SELECT deptno FROM emp GROUP BY deptno, job,
3,
5
]
{code}
When you are looking at a parenthesized expression it's difficult to tell
whether it's going to be a query:
{code:java}
ARRAY [
(((1 + 2) * 3) + 4),
((SELECT deptno FROM dept1
UNION
SELECT deptno FROM dept2)
EXCEPT
SELECT deptno FROM emp)
]
{code}
I agree we probably we should allow a scalar subquery (i.e. query enclosed in
parentheses, that returns 0 or 1 rows) as an item in ARRAY. It's just hard to
avoid ambiguous grammar.
> Parse error when using scalar sub-query as operand to Array constructor
> function
> --------------------------------------------------------------------------------
>
> Key: CALCITE-6508
> URL: https://issues.apache.org/jira/browse/CALCITE-6508
> Project: Calcite
> Issue Type: Bug
> Reporter: Ian Bertolacci
> Assignee: Ian Bertolacci
> Priority: Major
> Labels: pull-request-available
>
> Using a scalar subquery in the {{`ARRAY[ ... ]`}} function throws "parse
> failed: Query expression encountered in illegal context"
> (Calcite version 1.36)
> For example:
> {code:sql}
> select ARRAY[ (select 1) ]
> select ARRAY[ (select max(x) from table) ]
> {code}
> Is this something that can be configured or easily altered?
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