Question

非常感谢任何帮助。

我有一家餐桌医院：

加入后

Nurse + Year + No.Patients A001 |2000 | 23 A001 |2001 | 30 A001 |2002 | 35 B001 |2000 | 12 B001 |2001 | 15 B001 |2002 | 45 C001 |2000 | 50 C002 |2001 | 59 C003 |2002 | 69 etc



What I am trying to do is work out which nurse 
had the greatest increase of patients for the years 2000 - 2002.

Clearly B001 did as her patients increased from 12 to 45 and increase of 33
and what I am trying to produce is the result B001 | 33.

This is what I have so far:

select a.nurse,a.nopats from hospital as a
  join
    ( select nurse,max(nopats)-min(nopats) as growth
        from hospital where year between 2000 and 2002 group by nurse ) as s1
  on a.nurse = s1.nurse and a.nopats = s1.growth
  where year between 2000 and 2002;


but all I get returned is an empty set.

B001 | 33。

这里的任何帮助都会很棒。

谢谢！

Answer 1

试试这个：

SELECT nurse, (max(nopats) - min(nopats)) AS growth
  FROM hospital
 WHERE year BETWEEN 2000 AND 2002
 GROUP BY nurse
 ORDER BY growth DESC
LIMIT 1;

结果：B001 | 33由于LIMIT 1;如果你想要更多的结果，就把它留下吧。

Answer 2

SELECT nurse, MAX(nopats) - MIN(nopats) AS Growth
  FROM hospital 
 WHERE year BETWEEN 2000 AND 2002
 GROUP BY nurse
 ORDER BY Growth

应该这样做。如果那就是你需要的，请告诉我。

从查询返回的空集

2 个答案: