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The ALL/ANY subqueries are the subject of MIN/MAX optimization. The matter of this optimization is to embed MIN() or MAX() function into the subquery in order to get only one row by which we can tell whether the expression with ALL/ANY subquery is true or false. But when it is applied to a subquery like 'select a_constant' the reported bug occurs. As no tables are specified in the subquery the do_select() function isn't called for the optimized subquery and thus no values have been added to a MIN()/MAX() function and it returns NULL instead of a_constant. This leads to a wrong query result. For the subquery like 'select a_constant' there is no reason to apply MIN/MAX optimization because the subquery anyway will return at most one row. Thus the Item_maxmin_subselect class is more appropriate for handling such subqueries. The Item_in_subselect::single_value_transformer() function now checks whether tables are specified for the subquery. If no then this subselect is handled like a UNION using an Item_maxmin_subselect object. mysql-test/t/subselect.test: Added test case for bug#16302: Quantified subquery without any tables gives wrong results mysql-test/r/subselect.result: Added test case for bug#16302: Quantified subquery without any tables gives wrong results sql/item_subselect.cc: Fixed bug#16302: Quantified subquery without any tables gives wrong results The Item_in_subselect::single_value_transformer() function now checks whether tables are specified for the subquery. If no then this subselect is handled like a UNION using an Item_maxmin_subselect object.
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