SQL IN（）无法正常工作

Question

这是我的查询，但显示的结果是错误的。

SELECT winner 
FROM nobel 
WHERE 
    subject = 'Economics' AND 
    yr IN (
    SELECT min('yr') 
    FROM nobel 
    WHERE subject = 'Economics' 
); 

Answer 1

我相信这个问题是包裹yr的MIN()，这使得优化器地址里给出的报价为这会导致它被评价为MIN(constant_value)这始终是constant_value一个字符串。

尝试：

SELECT winner FROM nobel 
WHERE subject='Economics' 
     AND yr IN (SELECT min(yr) FROM nobel WHERE subject='Economics'); 

Answer 2

的问题是围绕yr单引号作为@sagi指出。我只是想指出的是，一个相关的条款是这样的查询与=一起比较典型的：

SELECT n.winner 
FROM nobel n 
WHERE n.subject = 'Economics' AND 
     n.yr = (SELECT min(yr) FROM nobel n2 WHERE n2.subject = n.subject); 

采用=与in这里看起来像一个小点给你。但是，=表示最多返回一行，in表示可能返回多行。这是SQL优化器的一个重要区别。

Answer 3

SELECT winner 
FROM nobel 
WHERE 
    subject = 'Economics' AND 
    yr IN (
     SELECT min(yr) # ---> just remove quotes in your query, it will work 
     FROM nobel 
     WHERE subject = 'Economics' 
    );