rA rA1不起作用，因为返回的指针将被销毁。 rA2工作正常，因为所有权的转移会保留对象。我的问题是unique_ptr。它是返回rA的别名，对吧？为什么不破坏对象，例如set @sql = null;
select group_concat( distinct
concat( ' sum(r.id= ', r.id,') as ID', r.id )
) into @sql
from Chat c
join Reason r on c.reason_id = r.id
where c.department_id = 1;
set @sql = concat('select ',@sql, '
from Chat c
join Reason r on c.reason_id = r.id
where c.department_id = 1');
prepare stmt from @sql;
execute stmt;
deallocate prepare stmt;
？