Stamatis Zampetakis created CALCITE-4702:
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             Summary: Error when executing query with GROUP BY constant via 
JDBC adapter
                 Key: CALCITE-4702
                 URL: https://issues.apache.org/jira/browse/CALCITE-4702
             Project: Calcite
          Issue Type: Bug
          Components: core, jdbc-adapter
    Affects Versions: 1.27.0
            Reporter: Stamatis Zampetakis
            Assignee: Stamatis Zampetakis


The following functionally equivalent SQL queries are accepted by Calcite and 
produce a valid plan 

{noformat}
select avg(salary) from employee group by true
select avg(salary) from employee group by 'a'
{noformat}

but they may fail if they are executed via the JDBC adapter since not all DBMS 
allow grouping by constants expressions. Moreover, what works for one may not 
work for the other. 

+Examples+
The {{GROUP BY TRUE}} query works in Postgres, and MySQL but fails in Redshift 
with the following exception:

{noformat}
com.amazon.redshift.util.RedshiftException: ERROR: non-integer constant in 
GROUP BY
{noformat}

The {{GROUP BY 'a'}} query works in MySQL but fails in Postgres with the 
following exception:

{noformat}
ERROR:  non-integer constant in GROUP BY
{noformat}

The {{GROUP BY}} constant essentially means {{GROUP BY}} nothing and there is a 
nice [blog 
post|https://blog.jooq.org/2018/05/25/how-to-group-by-nothing-in-sql/] listing 
some limitations of various DBMS. 



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