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https://issues.apache.org/jira/browse/CALCITE-6372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17868761#comment-17868761
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Mihai Budiu commented on CALCITE-6372:
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The one feature missing from this PR is the ability to do ASOF JOINs with USING.
The parser cannot handle that, the grammar seems to require too much lookahead
for that case. To support that the grammar may need to be refactored. But I
think that can be done in a separate PR.
> Support ASOF joins
> ------------------
>
> Key: CALCITE-6372
> URL: https://issues.apache.org/jira/browse/CALCITE-6372
> Project: Calcite
> Issue Type: New Feature
> Components: core
> Affects Versions: 1.36.0
> Reporter: Mihai Budiu
> Assignee: Mihai Budiu
> Priority: Minor
> Labels: pull-request-available
>
> Seems that this new kind of JOIN named AS OF is very useful for processing
> time-series data. Here is some example documentation from Snowflake:
> https://docs.snowflake.com/en/sql-reference/constructs/asof-join
> The semantics is similar to a traditional join, but the result always
> contains at most one record from the left side, with the last​ matching
> record on the right side (where "time" is any value that can be compared for
> inequality). This can be expressed in SQL, but it looks very cumbersome,
> using a JOIN, a GROUP BY, and then an aggregation to keep the last value.
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