Question

想到我自己学习SQL并开始使用

我正在练习一些教程并陷入一个基本查询。

在尝试了很多次后，我无法让它运行。

问题是：在哪些年份获得了物理奖，但没有获得化学奖。

这是我试过的

SELECT yr 
FROM nobel
WHERE subject ='Physics' AND
NOT (Select yr from nobel where subject = 'Chemistry')

有人可以提供帮助。

Answer 1

SELECT yr 
FROM nobel
WHERE subject ='Physics' AND
yr NOT IN (Select yr from nobel where subject = 'Chemistry')

Answer 2

如此接近！您只需要yr和IN：

SELECT yr 
FROM nobel
WHERE subject ='Physics' AND
    yr NOT IN (Select yr from nobel where subject = 'Chemistry')

您也可以使用排除联接执行此操作：

SELECT yr
FROM nobel n1
LEFT JOIN nobel n2 ON n1.yr = n2.yr AND n2.subject = 'Chemistry'
WHERE n1.subject = 'Physics' AND n2.subject is NULL

或NOT EXISTS

SELECT yr 
FROM nobel n1
WHERE n1.subject ='Physics' 
  AND NOT EXISTS 
  (
      SELECT NULL 
      FROM nobel n2 
      WHERE n2.subject = 'Chemistry' AND n2.yr=n1.yr
  )

Answer 3

您还可以使用LEFT [OUTER] JOIN，以确保同一年内不存在任何行：

SELECT yr 
FROM   nobel p
LEFT   JOIN nobel c ON c.yr = p.yr
                   AND c.subject = 'Chemistry'
WHERE  p.subject = 'Physics'
AND    c.yr IS NULL;

基本上有4种技术：

Select rows which are not present in other table

Answer 4

我相信你不需要第二个AND条件;因为第二个条件，您只是想要排除yr为subject的所有chemistry。您的查询可以只是

SELECT yr 
FROM nobel
WHERE subject ='Physics'

Answer 5

试试这个：

SELECT yr 
FROM nobel
WHERE subject ='Physics' AND yr
NOT IN(Select yr from nobel where subject = 'Chemistry') GROUP BY yr desc

Answer 6

省略

NOT（从诺贝尔选择主题='化学'）

因为你只是在寻找以Physics为主题的行。您不需要NOT查询，因为sql查询会自动省略Chemistry。

Answer 7

SELECT yr 
FROM nobel
WHERE subject ='Physics' AND subject <> 'Chemistry'

------------或者您可以尝试以下---------------------------

SELECT yr 
FROM nobel
WHERE subject ='Physics'

except

SELECT yr 
FROM nobel
WHERE subject ='Chemistry'

简单的SELECT SQL查询无效

7 个答案: