SQL查询:3个表的最高值加上行的其余部分
SQL查询:3个表的最高值加上行的其余部分
提问于 2017-12-22 09:53:24
目前，我一直在使用sql查询，试图找到解决方案，但现在让我头疼的是两次停留。我有三张桌子
用户表：
+-----+----------+-----------+
| pid | username | role |
+-----+----------+-----------+
| 1 | user1 | patient |
| 2 | user2 | patient |
| 3 | user3 | doc |
| 4 | user4 | assistant |
| 5 | user5 | patient |
+-----+----------+-----------+基地：
+-----+---------+-------+------------+
| pid | surname | name | birthdate |
+-----+---------+-------+------------+
| 1 | smith | john | 1950-07-31 |
| 2 | jackson | sarah | 1948-08-15 |
+-----+---------+-------+------------+医学博士：
+-----+-----+---------------+--------+--------+
| mid | pid | dateLastEntry | weight | pulse |
+-----+-----+---------------+--------+--------+
| 1 | 1 | 2017-12-01 | 86 | 65 |
| 2 | 1 | 2017-12-02 | 84 | 70 |
| 3 | 1 | 2017-12-03 | 80 | 67 |
| 4 | 2 | 2017-11-15 | 66 | 60 |
| 5 | 2 | 2017-11-17 | 60 | 64 |
+-----+-----+---------------+--------+--------+我试图为每个有角色病人的用户获取最大值(DateLastEntry)，显示他们的pid、姓名、姓氏、体重、脉搏--即使病人没有医学数据输入:如下所示：
+-----+---------+-------+------------+--------+-------+
| pid | surname | name | lastEntry | weight | pulse |
+-----+---------+-------+------------+--------+-------+
| 1 | smith | john | 2017-12-02 | 84 | 70 |
| 2 | jackson | sarah | 2017-11-17 | 60 | 64 |
| 5 | NONE | NONE | NONE | NONE | NONE |
+-----+---------+-------+------------+--------+-------+Atm我的声明看起来是这样的，但无法得到正确的结果：
select b.pid, s.surname, s.name, max(m.date) as lastEntry, m.weight, m.pulse
from users b
left join med-dat m on b.pid = m.pid
left join base-dat s on m.pid = s.pid
where b.role = 'Patient'
group by b.pid, s.surname, s.name, m.weight;回答 1
Stack Overflow用户
回答已采纳
发布于 2017-12-22 10:02:04
您可以如下所示重写查询，以获得所需的输出
select b.pid, s.surname, s.name, m.dateLastEntry as lastEntry, m.weight, m.pulse
from users b
left join med_dat m on b.pid = m.pid
left join base_dat s on m.pid = s.pid
left join med_dat m1 on m.pid = m1.pid
and m.dateLastEntry < m1.dateLastEntry
where m1.pid is null
and b.role = 'Patient'演示
从注释中编辑，使用用户表中的pid连接base_dat
select b.pid, s.surname, s.name, m.dateLastEntry as lastEntry, m.weight, m.pulse
from users b
left join med_dat m on b.pid = m.pid
left join base_dat s on b.pid = s.pid
left join med_dat m1 on m.pid = m1.pid and m.dateLastEntry < m1.dateLastEntry
where m1.pid is null
and b.role = 'Patient'
group by b.pid, s.surname, s.name, m.weight;演示
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/47939380
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