Question

所有这里都是一个MySQL问题，它使用来自2表连接的结果，有条件地评估它们并输出2个值。

这是数据库结构。

第一个表格gtpro包含

用户ID（列名称ID）

样本/年份数，即2年，4年或12年/年（列名labSamples__yr）

第二桌实验结果包含

相同的用户ID（列名idgtpro）

和样本日期的日期列（提供样本时）列名称日期

因此，此查询会返回所有ID的概述以及为该ID提交的最后一个样本的时间。

SELECT a.id, a.labSamples__yr, max(b.date) as ndate from gtpro as a 
join labresults as b on a.id = b.idgtpro group by a.id

我要评估的条件是这样的。

a.labSamples__yr = 2 and ndate >= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)
a.labSamples__yr = 4 and ndate >= DATE_SUB(CURDATE(), INTERVAL 3 MONTH)
a.labSamples__yr = 12 and ndate >= DATE_SUB(CURDATE(), INTERVAL 1 MONTH)

因此，如果样本数/年为2且最后一个samle日期超过6个月，我想知道该id的样本的id和最新日期。

我尝试过使用CASE和IF语句，但不能正确使用它。这是我最近的尝试。

select id, ndate,
case when (labSamples__yr = 2 and ndate <= DATE_SUB(CURDATE(), INTERVAL 6 MONTH))is true
then
(SELECT id from gtpro as a join labresults as b on a.id = b.idgtpro where
labSamples__yr = 2 and max(b.date) <= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)) end as id
from (SELECT a.id, a.labSamples__yr, max(b.date) as ndate from gtpro as a 
join labresults as b on a.id = b.idgtpro group by a.id) d

这告诉我无效使用群组功能。

急需一点帮助

编辑我搞砸了上面代码中的一些名字，我现在修复了这些名字。

Answer 1

这是否意味着有效的MySQL？我不知道＆＃34;是真的＆＃34;在CASE声明中有效。公平地说，虽然我对Oracle和SQL Server比较熟悉，但是......这个陈述的任何部分都有用吗？

修改

好的，这是我编辑代码的原因：

select id, ndate, case when (labSamples__yr = 2 and ndate <= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)) then (SELECT id from bifipro as a join labresults as b on a.id = b.idBifipro where labSamples__yr = 2 and max(b.date) <= DATE_SUB(CURDATE(), INTERVAL 6 MONTH) where a.id=d.id) end as id from (SELECT a.id, a.labSamples__yr, max(b.date) as ndate from bifipro as a join labresults as b on a.id = b.idBifipro group by a.id) d

在您的相关子查询中，我添加了 ＆＃34;的谓词，其中a.id = d.id＆＃34;

我已从您的个案陈述中删除 ＆＃34;是真的＆＃34; 不正确，但我没有＆＃39;认为应该在那里。

Answer 2

如果我理解你的问题，你应该能够把条件放在where条款中：

SELECT a.id, a.labSamples__yr, max(b.date) as ndate
from gtpro a join
     labresults b
     on a.id = b.idgtpro
where (a.labSamples__yr = 2 and b.date >= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)) or
      (a.labSamples__yr = 4 and b.date >= DATE_SUB(CURDATE(), INTERVAL 3 MONTH)) or
      (a.labSamples__yr = 12 and b.date >= DATE_SUB(CURDATE(), INTERVAL 1 MONTH))
group by a.id;

这可以解决您的语法问题。但是，如果您希望id具有最大日期，请尝试执行以下操作：

select a.labSamples__yr, max(b.date) as ndate,
       substring_index(group_concat(a.id order by b.date desc)) as maxid
from gtpro a join
     labresults b
     on a.id = b.idgtpro
where (a.labSamples__yr = 2 and b.date >= DATE_SUB(CURDATE(), INTERVAL 6 MONTH)) or
      (a.labSamples__yr = 4 and b.date >= DATE_SUB(CURDATE(), INTERVAL 3 MONTH)) or
      (a.labSamples__yr = 12 and b.date >= DATE_SUB(CURDATE(), INTERVAL 1 MONTH))
group by a.labSamples__yr;

将a.id放在group by中并不会为您提供任何内容的最大ID。

Answer 3

答案部分受到Tomas的启发（sql澄清和语法澄清）我一起摆脱了CASE。这对我来说似乎很好，但我想听听任何其他建议

select id, labSamples__yr, ndate from
(SELECT a.id, a.labSamples__yr, max(b.date) as ndate from gtpro as a 
join labresults as b on a.id = b.idgtpro  group by a.id)d 
where (ndate <= DATE_SUB(CURDATE(), INTERVAL 6 MONTH) and labSamples__yr = 2) 
or (ndate <= DATE_SUB(CURDATE(), INTERVAL 3 MONTH) and labSamples__yr = 4)
or (ndate <= DATE_SUB(CURDATE(), INTERVAL 1 MONTH) and labSamples__yr = 12)

感谢您的期待，但是看到使用CASE语句的解决方案以供日后参考仍然很高兴

MySQL在连接表中使用IF或CASE语句

3 个答案: