T-SQL遊標或者或情況下

Question

我有這個表：

Table_NAME_A：

quotid itration QStatus    
-------------------------------- 
5329 1   Assigned         
5329 2   Inreview         
5329 3   sold           
4329 1   sold      
4329 2   sold      
3214 1   assigned     
3214 2   Inreview 

結果輸出應該是這樣的：

quotid itration QStatus 
------------------------------   
5329 3   sold      
4329 2   sold      
3214 2   Inreview 

T-SQL查詢，所以基本上我希望數據處於「已售出」狀態（如果不存在），那麼如果不存在，那麼「未檢查」然後「已分配」，並且同時如果「已售出」或「檢查」或「已分配」具有多次迭代，那麼我希望最高「迭代」。

請幫助我，在此先感謝:)

Answer 1

你既不希望遊標也不希望/然後爲此。相反，您將使用一系列自連接來獲得這些結果。我也將使用一個CTE來簡化獲取最大迭代的每一步：

with StatusIterations As 
(
    SELECT quotID, MAX(itration) Iteration, QStatus 
    FROM table_NAME_A 
    GROUP BY quotID, QStats 
) 
select q.quotID, coalesce(sold.Iteration,rev.Iteration,asngd.Iteration) Iteration, 
       coalesce(sold.QStatus, rev.QStatus, asngd.QStatus) QStatus 
from 
    --initial pass for list of quotes, to ensure every quote is included in the results 
    (select distinct quotID from table_NAME_A) q 
--one additional pass for each possible status 
left join StatusIterations sold on sold.quotID = q.quotID and sold.QStatus = 'sold' 
left join StatusIterations rev on rev.quotID = q.quotID and rev.QStatus = 'Inreview' 
left join StatusIterations asngd on asngd.quotID = q.quotID and asngd.QStatus = 'assigned' 

如果您有等同於數值的狀態的表，可以進一步對這個改善：

表：狀態

 
QStatus Sequence 
'Sold'  3 
'Inreview' 2 
'Assigned' 1

和代碼變爲：

select t.quotID, MAX(t.itration) itration, t.QStatus 
from 
(
    select t.quotID, MAX(s.Sequence) As Sequence 
    from table_NAME_A t 
    inner join Status s on s.QStatus = t.QStatus 
    group by t.quotID 
) seq 
inner join Status s on s.Sequence = seq.Sequence 
inner join table_NAME_A t on t.quotID = seq.quotID and t.QStatus = s.QStatus 
group by t.quoteID, t.QStatus 

上面看起來可能看起來很複雜，但它可以更快，並且可以在不更改代碼的情況下輕鬆擴展超過三種狀態。

Answer 2

這是一個優先級查詢。要做到這一點的方法之一是在union all連續的比較：

select a.* 
from table_a a 
where quote_status = 'sold' 
union all 
select a.* 
from table_a a 
where quote_status = 'Inreview' and 
     not exists (select 1 from table_a a2 where a2.quoteid = a.quoteid and a2.quotestatus = 'sold') 
union all 
select a.* 
from table_a a 
where quote_status = 'assigned' and 
     not exists (select 1 
        from table_a a2 
        where a2.quoteid = a.quoteid and a2.quotestatus in ('sold', 'Inreview') 
       ); 

有關較大的一組數據的表現，你會想在table_a(quoteid, quotestatus)的索引。