The SQL standard doesn't allow to use in HAVING clause fields that are not 
present in GROUP BY clause and not under any aggregate function in the HAVING
clause. However, mysql allows using such fields. This extension assume that 
the non-grouping fields will have the same group-wise values. Otherwise, the 
result will be unpredictable. This extension allowed in strict 
MODE_ONLY_FULL_GROUP_BY sql mode results in misunderstanding of HAVING 
capabilities.

The new error message ER_NON_GROUPING_FIELD_USED message is added. It says
"non-grouping field '%-.64s' is used in %-.64s clause". This message is
supposed to be used for reporting errors when some field is not found in the
GROUP BY clause but have to be present there. Use cases for this message are 
this bug and when a field is present in a SELECT item list not under any 
aggregate function and there is GROUP BY clause present which doesn't mention 
that field. It renders the ER_WRONG_FIELD_WITH_GROUP error message obsolete as
being more descriptive.
The resolve_ref_in_select_and_group() function now reports the 
ER_NON_GROUPING_FIELD_FOUND error if the strict mode is set and the field for 
HAVING clause is found in the SELECT item list only.