Question

我有一个数据表，看起来像这样：

ID Num | Code
-------------
   1   |   A
   1   |   B
   1   |   C
   1   |   D
   2   |   A
   2   |   B
   3   |   A
   3   |   B
   3   |   D
   4   |   B
   5   |   A
   5   |   B
   5   |   E

我需要能够编写一个SQL查询来向我显示所有没有与之关联的代码C或D的ID号。（在此示例中将是ID号码2,4和5）。

提前感谢您提供的任何帮助！

Answer 1

我会使用NOT IN：

void Graphics::UpdateLight() {
    short radius = 65; // 265 on the pictures

    int x = m_game->GetPlayer()->GetSprite()->getPosition().x + CASE_LEN / 2; // Setting on the middle of the player sprite (CASE_LEN is a const which contains the size of a case (here 32))
    int y = HEIGHT - (m_game->GetPlayer()->GetSprite()->getPosition().y + CASE_LEN / 2); // (the "HEIGHT -" part was set because it seems that y = 0 is on the bottom of the texture for GLSL)

    sf::Vector3f shaderLight;
    shaderLight.x = x;
    shaderLight.y = y;
    shaderLight.z = radius;

    m_lightShader.setParameter("light", shaderLight);
}

Answer 2

我喜欢使用group by和having来解决此类问题：

select id_num
from t
group by id_num
having sum(case when code in ('C', 'D') then 1 else 0 end) = 0;

Answer 3

你可以使用'not exists'（通常更有效率）

SELECT DISTINCT ID_Num
FROM yourtable f1
WHERE not exists
(
    SELECT * FROM yourtable f2 
    WHERE f2.code in ('C', 'D') and f2.ID_Num=f1.ID_Num
)

Answer 4

你可以使用'left outer join lateral'并且不使用这样的行：

{{1}}

查询以识别没有特定值的记录

4 个答案: