Question

我的表格是这样的：

ID|EID|priority|completed_forms|all_forms_in
1 |78 |NULL    |y              |y
2 |24 |NULL    |y              |y
3 |78 |1       |y              |y

我想要完成的任务： 如果它们共享相同的EID，则只选择行，并且所有行共享优先级为NULL，并且对于completed_forms和all_forms_in标记为“y”。

我尝试了什么：这是我当前的选择声明：

SELECT * FROM tasks 
WHERE priority IS NULL AND EID in 
(
SELECT * FROM 
    (select EID from tasks 
    WHERE completed_form = 'y' AND all_forms_in = 'y' ) as priority_check
GROUP BY EID having count(*) = 2
)

预期结果： 我希望这返回NO行，因为只有当两个行都为NULL时，select才能确保返回。在这种情况下，ID 1和ID 3都不共享NULL。相反，它返回ID 1。

Answer 1

您可以添加AND COUNT(priority) = 0（COUNT，字段名称不计算空值），如下所示：

SELECT EID FROM tasks 
GROUP BY EID HAVING 
  COUNT(priority) = 0 AND
  COUNT(DISTINCT completed_form) = 1 AND MAX(completed_form) = 'y' AND
  COUNT(DISTINCT all_forms_in) = 1 AND MAX(all_forms_in) = 'y'AND
  COUNT(*) = 2

MySQL - 仅当组中的所有组都为NULL时才选择

1 个答案: