Jark Wu created CALCITE-1917:
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             Summary: Support column reference in "FOR SYSTEM_TIME AS OF"
                 Key: CALCITE-1917
                 URL: https://issues.apache.org/jira/browse/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:

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

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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