Question

我正在尝试运行查询以根据另一个名为pro_details的表中的日期显示名为products的表中的最大值和最小值。查询应显示该特定日期的最多购买产品以及最少产品购买。但是，即使实际日期存在，查询也不会显示给定月份的任何记录！

SELECT 
    Prod.delivered, MIN(quality) Low, MAX(quality) High 
FROM 
    pro_details prod, products pro
WHERE 
    pro.ord = pro.ord
    AND Prod.delivered = TO_DATE('12-2015','mm-yyyy')
GROUP BY  
    Prod.delivered
ORDER BY  
    Prod.delivered DESC;

Answer 1

SQL日期比较完全。如果您只在日期中包含月份和年份，则比较假定您要对DateTime值中的所有剩余组件使用零。您正在对仅在该月的第一个时刻记录日期的记录进行精确比较。

如果你想要整个月，你需要检查整个范围，从月初到月末：

SELECT Prod.delivered, MIN(quality) Low, MAX(quality) High 
FROM pro_details prod, products pro
WHERE pro.ord = pro.ord
  AND  Prod.delivered >= TO_DATE('12-2015','mm-yyyy')
  AND  Prod.delivered <  TO_DATE('01-2016','mm-yyyy')
GROUP BY  Prod.delivered
ORDER BY Prod.delivered DESC;

Answer 2

你错过了where子句附近的'd'，并且还必须将传递的字段转换为'mm-yyyy'字符串格式。试试这个：

SELECT Prod.delivered, MIN(quality) Low, MAX(quality) High 
FROM pro_details prod, products pro
WHERE prod.ord = pro.ord
AND  TO_CHAR(Prod.delivered,'mm-yyyy') = '12-2015'
GROUP BY  Prod.delivered
ORDER BY Prod.delivered DESC;

修订查询：

SELECT pro.ord, quality
from pro_details prod, products pro
where prod.ord = pro.ord
AND TO_CHAR(Prod.delivered,'mm-yyyy') = '12-2015'
GROUP BY pro.ord, quality
having quality=min(quality) or quality=max(quality)

高和低值sql

2 个答案: