```
play-eu :) SELECT actor_login, event_type, count() FROM github_events WHERE repo_name = 'ClickHouse/ClickHouse' GROUP BY actor_login, event_type WITH ROLLUP ORDER BY count() DESC LIMIT 10

SELECT
    actor_login,
    event_type,
    count()
FROM github_events
WHERE repo_name = 'ClickHouse/ClickHouse'
GROUP BY
    actor_login,
    event_type
    WITH ROLLUP
ORDER BY count() DESC
LIMIT 10

Query id: 1b7baa06-2ee6-4ae8-b1ed-4c9ecb21514c

Ok.
Exception on client:
Code: 36. DB::Exception: Code: 36. DB::Exception: Unexpected value 0 in enum. (BAD_ARGUMENTS) (version 22.5.1.1984 (official build)). (BAD_ARGUMENTS)
```
/** Values of data type can be summed (possibly with overflow, within the same data type).
      * Example: numbers, even nullable. Not Date/DateTime. Not Enum.
      * Enums can be passed to aggregate function 'sum', but the result is Int64, not Enum, so they are not summable.
      */
    virtual bool isSummable() const { return false; }
    /** Can be used in operations like bit and, bit shift, bit not, etc.
      */
    virtual bool canBeUsedInBitOperations() const { return false; }
    /** Can be used in boolean context (WHERE, HAVING).
      * UInt8, maybe nullable.
      */
    virtual bool canBeUsedInBooleanContext() const { return false; }
    /** Numbers, Enums, Date, DateTime. Not nullable.
      */
    virtual bool isValueRepresentedByNumber() const { return false; }
    /** Integers, Enums, Date, DateTime. Not nullable.
      */
    virtual bool isValueRepresentedByInteger() const { return false; }
    /** Unsigned Integers, Date, DateTime. Not nullable.
      */
    virtual bool isValueRepresentedByUnsignedInteger() const { return false; }
    /** Values are unambiguously identified by contents of contiguous memory region,
      *  that can be obtained by IColumn::getDataAt method.
      * Examples: numbers, Date, DateTime, String, FixedString,
      *  and Arrays of numbers, Date, DateTime, FixedString, Enum, but not String.
      *  (because Array(String) values became ambiguous if you concatenate Strings).
      * Counterexamples: Nullable, Tuple.
      */
    virtual bool isValueUnambiguouslyRepresentedInContiguousMemoryRegion() const { return false; }