SQL返回从多个密钥

Question

的铅丹值这是迄今为止我已经写了我的查询代码：

 select 
     workorderkey, 
     WarrantyRoutingStep, 
     StepOrder 
    from tblFAWOWarrantyRoutingsOEM WarrantyRoutings 
    where 
workorderkey=220870 and --fyi i do not want to do this 
StepCompleteDate IS NULL 

结果是这样的

Current Output

我如何得到它看起来像这样，所以它只返回StepOrder列中具有最小值的那一行）？请注意，我不只想要workorderkey 220870的结果;我希望它对每个工单进行分组和返回一个结果 - 只需输入该过滤器进行测试即可。

Desired Output

请原谅图片代替文字表结果。第一次海报，一个月的观众。刚刚几周前开始编写SQL。

Answer 1

select 
    min(StepOrder), 
    workorderkey, 
    WarrantyRoutingStep 
from tblFAWOWarrantyRoutingsOEM WarrantyRoutings 
where StepCompleteDate IS NULL 
GROUP BY workorderkey, WarrantyRoutingStep 

这会为你工作

Answer 2

如果你的DBMS支持窗口的功能很简单：

SELECT * 
FROM 
    (
     select 
      workorderkey, 
      WarrantyRoutingStep, 
      StepOrder, 
      ROW_NUMBER() OVER (PARTITION BY workorderkey ORDER BY StepOrder) as RowNumber 
     from tblFAWOWarrantyRoutingsOEM WarrantyRoutings 
     where StepCompleteDate IS NULL 
    ) t 
WHERE 
    t.RowNumber = 1 

无窗的功能，你还可以这样做：

SELECT wr2.* 
FROM 
    (
     select 
      workorderkey, 
      MIN(StepOrder) as MinStepOrder 
     from tblFAWOWarrantyRoutingsOEM WarrantyRoutings 
     where StepCompleteDate IS NULL 
     GROUP BY 
      workorderkey 
    ) t 
    INNER JOIN tblFAWOWarrantyRoutingsOEM wr2 
    On t.workorderkey = wr2.workorderkey 
    AND StepCompleteDate IS NULL 

但如果每个工单的“步序”不唯一，则后面的方法仍然可能与关系结束。