[jira] [Created] (CALCITE-3081) Literal NULL should be generated in SqlDialect

["Feng Zhu (JIRA)" <ji...@apache.org>]

Feng Zhu created CALCITE-3081:
---------------------------------

             Summary: Literal NULL should be generated in SqlDialect
                 Key: CALCITE-3081
                 URL: https://issues.apache.org/jira/browse/CALCITE-3081
             Project: Calcite
          Issue Type: Bug
    Affects Versions: 1.19.0
            Reporter: Feng Zhu


In Calcite, this simple query will throw exception during validation, even it is ok in many databases. 
{code:java}
Query:
final String query = "select NULL as col "
    + "from \"foodmart\".\"product\"";

Exception
org.apache.calcite.tools.ValidationException: org.apache.calcite.runtime.CalciteContextException: From line 1, column 8 to line 1, column 11: Illegal use of 'NULL'
{code}
The right way to use 'NULL' in Calcite is:
{code:java}
final String query = "select cast(NULL as integer) as col "
    + "from \"foodmart\".\"product\"";
{code}
However,  the converted query by *RelToSqlConverter* is illegal in Calcite again.
{code:java}
SELECT NULL AS \"COL\"
FROM \"foodmart\".\"product\"
{code}
The issue is trivial, but it is against to general sense. Maybe we can generate NULL literal in SqlDialect?



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