Sql 如果有多个列，则查询不选择列

我一直在为这事挠头

对于同一个项目，我有一个包含多个列的表。 但是，每个项目可以有多个不同类型的行

我只想找到类型为O的项目，并且只有当它们没有其他类型与之关联时

例：

在上述情况下，只应返回项目2

是否有查询或方法来筛选此信息？欢迎提供任何建议。

您可以使用“不存在”来执行此操作：

您还可以使用聚合来执行此操作：

select p.project_num
from projects p
group by p.project_num
having sum(case when p.type = 'O' then 1 else 0 end) > 0 and
       sum(case when p.type <> 'O' then 1 else 0 end) = 0;

您可以使用“不存在”来执行此操作：

您还可以使用聚合来执行此操作：

select p.project_num
from projects p
group by p.project_num
having sum(case when p.type = 'O' then 1 else 0 end) > 0 and
       sum(case when p.type <> 'O' then 1 else 0 end) = 0;

---

如果我理解正确，您希望检查项目是否只有其项目编号的记录，并且其类型为“O”。您可以使用以下查询来实现此功能：

;with cte_proj as
(
select Project_Num from YourTable    
group by Project_Num
having count(Project_Num) = 1)
select Project_Num from cte_proj c
inner join YourTable t on c.Project_Num = t.Project_Num
where t.Type = 'O'

---

如果我理解正确，您希望检查项目是否只有其项目编号的记录，并且其类型为“O”。您可以使用以下查询来实现此功能：

;with cte_proj as
(
select Project_Num from YourTable    
group by Project_Num
having count(Project_Num) = 1)
select Project_Num from cte_proj c
inner join YourTable t on c.Project_Num = t.Project_Num
where t.Type = 'O'

---

另一个选择相当快

SELECT p0.*
FROM project p0
  LEFT JOIN project p1 ON (p0.Type<>p1.Type AND p0.Project_Num=p1.Project_Num)
WHERE p0.Type='O' AND p1.Type IS NULL;

---

另一个选择相当快

SELECT p0.*
FROM project p0
  LEFT JOIN project p1 ON (p0.Type<>p1.Type AND p0.Project_Num=p1.Project_Num)
WHERE p0.Type='O' AND p1.Type IS NULL;

---

谢谢，我试试看谢谢，我试试看