Question

SELECT DISTINCT( m.pm_name ) 
FROM   prime_minister AS m, 
       prime_minister AS p 
WHERE  m.state_born IS NOT NULL 
GROUP  BY m.pm_name, 
          m.birth_yr 
HAVING m.birth_yr = (SELECT Min(p.birth_yr) 
                     FROM   prime_minister)

我的问题如下：

该查询应该产生出生于澳大利亚的第一位总理......因此WHERE m.state_born IS NOT NULL

Answer 1

为什么要在子查询中引用外部表？写一个像这样的简单子查询。

SELECT DISTINCT pm_name 
FROM prime_minister 
WHERE state_born IS NOT NULL 
AND birth_yr = (SELECT MIN(birth_yr) FROM prime_minister)

Answer 2

不确定我完全理解你的问题。但我根本没有找到group by或having的原因：

SELECT m.pm_name
FROM   prime_minister
WHERE  m.state_born IS NOT NULL 
AND    m.birth_yr = (SELECT Min(p.birth_yr) 
                     FROM   prime_minister p
                     WHERE  p.state_born IS NOT NULL)

Answer 3

这有用吗？

SELECT TOP 1 pm_name, MIN(birth_yr)
FROM   prime_minister
WHERE  birth_yr IS NOT NULL 
GROUP BY pm_name
ORDER BY pm_name, MIN(birth_yr)

Answer 4

我认为你正试图找到在每个州出生的第一位总理：

select pm_name, state_born from prime_minister m
inner join 
(
    select min(birth_yr) birth_yr, state_born
    from prime_minister
    where state_born is not null
    group by state_born
)
t
on m.state_born = t.state_born and m.birth_yr = t.birth_yr

Answer 5

使用EXISTS（）运算符

尝试选项

SELECT m.pm_name
FROM prime_minister AS m     
WHERE EXISTS (
              SELECT 1
              FROM prime_minister p
              WHERE p.state_born IS NOT NULL
              HAVING MIN(p.birth_yr) = m.birth_yr
              ) AND m.state_born IS NOT NULL

子查询返回的值超过1。这是不允许的......或者当子查询用作表达式时

5 个答案: