我的結果集優良似乎除了我得到我想要避免額外的重複的結果,這裏是這種情況:需要用複雜的查詢幫助
我用兩個表:
爲了
id|companyname|routeid|orderdate
1 |company1 | 23dsa |
2 |company1 | 23dsa | 2011-04-28
3 |company1 | 23dsa | 2011-04-05
4 |company2 | 24gcc | 2011-22-05
車輛
id| vehiclename | routeid
1 | van1 | 23dsa
2 | van2 | 24gcc
這是我的查詢1:
select t1.companyname, max(t1.orderdate) as orderdate
from order t1, vehicle t2 where t1.routeid=t2.routeid
group by t1.companyname, t1.orderdate
order by t1.id
這是查詢2:
select t1.companyname, max(t1.orderdate) as orderdate
from order t1, vehicle t2 where t1.routeid=t2.routeid
group by t1.companyname, t1.orderdate having count(1) = 1
order by t1.id
這是我的結果:
companyname | orderdate
company1 |
company1 | 2011-04-28
company1 | 2011-04-05
company2 | 2011-22-05
我想它是這樣的:
companyname | orderdate
company1 | 2011-04-28
company2 | 2011-22-05
我失蹤不爲空:
select t1.companyname, max(t1.orderdate) as orderdate
from order t1, vehicle t2 where t1.orderdate is not null and t1.routeid=t2.routeid
group by t1.companyname, t1.orderdate
order by t1.id
是否有您所涉及的第二個表什麼理由? – Henry 2011-05-11 22:37:17
@亨利是我只有那些匹配 – 2011-05-11 22:46:55