Question

我完全陷入了疑问。我有一个看起来像这样的查询：

select dr_machine, 
  dr_worker, 
  min(dr_date) as firstDate, 
  max(dr_date) as lastDate 
from data 
where dr_machine IS NOT NULL 
  && dr_worker IS NOT NULL 
group by dr_worker, dr_machine 
order by dr_machine;

结果将是：

+------------+-------------------+------------+------------+
| dr_machine | dr_worker         | firstDate  | lastDate   |
+------------+-------------------+------------+------------+
| KBA R-     | john              | 1242165600 | 1423350000 |
| KBA R-     | peter             | 1305237600 | 1316642400 |
| KBA R-     | philip            | 1248040800 | 1423522800 |
| Solna      | marie             | 1298453600 | 1378453600 |
| Solna      | laura             | 1278453600 | 1398453600 |
| Solna      | anne              | 1288453600 | 1388453600 |
+------------+-------------------+------------+------------+

我希望它显示dr_machine中的min和max dr_date，而不是dr_worker（就像现在一样）所以结果如下：

+------------+-------------------+------------+------------+
| dr_machine | dr_worker         | firstDate  | lastDate   |
+------------+-------------------+------------+------------+
| KBA R-     | john              | 1242165600 | 1423522800 |
| KBA R-     | peter             | 1242165600 | 1423522800 |
| KBA R-     | philip            | 1242165600 | 1423522800 |
| Solna      | marie             | 1278453600 | 1398453600 |
| Solna      | laura             | 1278453600 | 1398453600 |
| Solna      | anne              | 1278453600 | 1398453600 |
+------------+-------------------+------------+------------+

之前我将此结果与php中的另一个查询相结合，如下所示：

select dr_machine, 
  min(dr_date) as firstDate, 
  max(dr_date) as lastDate 
from data 
where dr_date IS NOT NULL 
group by dr_machine;

我尝试过不同的连接和子查询，但说实话，我不知道自己在做什么，结果永远不会成为我想要的结果。

祝你好运尼克拉斯

Answer 1

我不是100％了解你的问题，但我的猜测是：

select data.dr_machine, 
  data.dr_worker, 
  t.firstDate, 
  t.lastDate 
from data 
left join(
select dr_machine, 
  min(dr_date) as firstDate, 
  max(dr_date) as lastDate 
from data 
group by dr_machine ) as t
on data.dr_machine = t.dr_machine
where data.dr_machine IS NOT NULL 
  && data.dr_worker IS NOT NULL 
order by data.dr_machine,data.dr_worker

Answer 2

我首先编写一个查询，获取dr_machine的信息，就像你已经拥有的那样：

SELECT dr_machine, MIN(dr_date) AS firstDate, MAX(dr_date) AS lastDate
FROm data
WHERE dr_date IS NOT NULL
GROUP BY dr_machine;

然后，只需将该子查询与您的表一起加入dr_worker列：

SELECT d.dr_machine, d.dr_worker, tmp.firstDate, tmp.lastDate
FROM data d
JOIN(
   SELECT dr_machine, MIN(dr_date) AS firstDate, MAX(dr_date) AS lastDate
   FROM data
   WHERE dr_date IS NOT NULL
   GROUP BY dr_machine) tmp ON tmp.dr_machine = d.dr_machine AND dr_worker IS NOT NULL
GROUP BY d.dr_machine, d.dr_worker;

mysql - 按结果组获取最大结果

2 个答案: