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From "Jark Wu (JIRA)" <>
Subject [jira] [Created] (CALCITE-1917) Support column reference in "FOR SYSTEM_TIME AS OF"
Date Wed, 02 Aug 2017 02:31:00 GMT
Jark Wu created CALCITE-1917:

             Summary: Support column reference in "FOR SYSTEM_TIME AS OF"
                 Key: CALCITE-1917
             Project: Calcite
          Issue Type: New Feature
            Reporter: Jark Wu
            Assignee: Julian Hyde

you mean it can be covered by standard. I agree, the query I posted in the previous mail can
be rewrote as a subquery:

As discussed in mailing list[1], the standard says QSTPS can’t contain a column reference.
So when joining the Orders to the Products table for the price as of the time the order was
placed is impossible using "FOR SYSTEM_TIME AS OF". But can be expressed using a subquery,
such as:

    FROM Orders AS o
    JOIN LATERAL (SELECT * FROM ProductPrices WHERE sysStart <= O.orderTime AND sysEnd
> O.orderTime) AS P
      ON o.productId = p.productId

But subquery is too complex for users. We know that the standard says it can’t contain a
column reference. We initialize this discuss as we would like to "extend" the standard to
simplify such query. 

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