Question

我需要显示用户的出勤年份和月份。这是一个样本看起来如何-非常基本：

     Conversation_message::Sender()->first();

从单个表中检索数据，我尝试了以下查询为此：

Year - Jan - Feb
2018 - 26  - 20
2019 - 20  - 22

很遗憾，这不会返回预期的数据，而是显示年度用户每月的出勤情况如下：

SELECT EXTRACT(YEAR FROM M.DATE) "YEAR",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE)  = '1' THEN M.Id ELSE '-' END) "Jan",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE)  = '2' THEN M.Id ELSE '-' END) "Feb"
FROM TABLE m 
WHERE M.STATUS = 'P' AND M.Id = '12345678'
GROUP BY EXTRACT(YEAR FROM M.DATE) ORDER BY EXTRACT(YEAR FROM M.DATE);

我在这里错过了什么吗？任何想法将不胜感激。

Answer 1

试试这个-

SELECT EXTRACT(YEAR FROM M.DATE) "YEAR",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE)  = '1' THEN M.Id ELSE NULL END) "Jan",
COUNT(CASE WHEN EXTRACT(MONTH FROM M.DATE)  = '2' THEN M.Id ELSE NULL END) "Feb"
FROM TABLE m 
WHERE M.STATUS = 'P' AND M.Id = '12345678'
GROUP BY EXTRACT(YEAR FROM M.DATE) ORDER BY EXTRACT(YEAR FROM M.DATE);

OR-

SELECT EXTRACT(YEAR FROM M.DATE) "YEAR",
SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE)  = '1' THEN 1 ELSE 0 END) "Jan",
SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE)  = '2' THEN 1 ELSE 0 END) "Feb"
FROM TABLE m 
WHERE M.STATUS = 'P' AND M.Id = '12345678'
GROUP BY EXTRACT(YEAR FROM M.DATE) ORDER BY EXTRACT(YEAR FROM M.DATE);

Answer 2

我更喜欢使用SUM()。但更重要的是，您的代码是混合类型。 EXTRACT()返回一个数字，因此比较应该是一个数字。我建议：

SELECT EXTRACT(YEAR FROM M.DATE) as "YEAR",
       SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE) = 1 THEN 1 ELSE 0 END) as "Jan",
       SUM(CASE WHEN EXTRACT(MONTH FROM M.DATE) = 2 THEN 1 ELSE 0 END) as "Feb"
FROM TABLE m 
WHERE M.STATUS = 'P' AND
      M.Id = 12345678  -- I am guessing that `id` is also a number
GROUP BY EXTRACT(YEAR FROM M.DATE)
ORDER BY EXTRACT(YEAR FROM M.DATE);

您应该小心混合类型。转换可能会妨碍优化器找到最佳查询计划的能力。

用户出席日期年月明智

2 个答案: