Question

如何从最多日期

的3个表中获取数据

select 
    c.model_key, v.id, v.category_Id, v.Text1, v.Numeric1,
    c.Name, fx.Currency_code, fx.Rate, fx.effective_dt 
from 
    aps.v_m_fxrates fx 
join 
    aps.t_m_value v on fx.Currency_code = v.Text1 
join 
    aps.t_m_category c on v.Category_Id = c.Id 
where 
    c.Name = 'FXRates' 
    and c.Model_Key = 25 
    and v.Text1 = fx.Currency_code 
    and fx.version = 2

使用上面的查询我得到了结果，但结果出现在所有effective_dt上。而不是这个，我只需要选择最新effective_dt的记录。在下图中，有2条AED记录，其中最新日期为1999-03-31，必须返回。在此之后我不知道如何继续并进一步过滤结果以实现输出。

我也试过这个

select 
    c.model_key, v.id, v.category_Id, v.Numeric1,
    c.Name, fx.Currency_code, fx.Rate, fx.effective_dt 
from 
    aps.v_m_fxrates fx 
join 
    aps.t_m_value v on fx.Currency_code = v.Text1 
join 
    aps.t_m_category c on v.Category_Id = c.Id 
where 
    c.Name = 'FXRates' 
    and c.Model_Key = 25 
    and v.Text1 = fx.Currency_code 
    and fx.version = 2 
    and fx.effective_dt in (select MAX(effective_dt) 
                            from aps.v_m_fxrates)

但没有回复。

实际输出：

预期产出：

Answer 1

在子查询中使用 row_number（） 函数，如下所示：

select 
     c.model_key, v.id, v.category_Id, v.Text1, v.Numeric1,
     c.Name, fx.Currency_code, fx.Rate, fx.effective_dt 
from (
    select
         Currency_code,Rate,effective_dt
        ,SeqNo = row_number() over (partition by Currency_code order by effective_dt desc)
    from aps.v_m_fxrates 
    where version = 2
) fx 
join 
    aps.t_m_value v on fx.Currency_code = v.Text1 
join 
    aps.t_m_category c on v.Category_Id = c.Id 
where c.Name = 'FXRates' 
  and c.Model_Key = 25 
  and v.Text1 = fx.Currency_code 
  and fx.SeqNo = 1

Answer 2

尝试使用运算符 TOP 1 和相应的 ORDER BY

例如：

SELECT TOP 1 C.model_key,
             V.id,
             ...
FROM ...
ORDER BY FX.effective_dt DESC

您拥有的另一个选项是在where子句中使用聚合函数和相关性。

select C.model_key,
       V.id,
       V.category_Id, 
       V.Text1,
       V.Numeric1,
       C.Name, 
       FX.Currency_code,
       FX.Rate,
       FX.effective_dt 
FROM aps.v_m_fxrates AS FX
    JOIN aps.t_m_value AS V on FX.Currency_code = V.Text1 
    JOIN aps.t_m_category AS C on V.Category_Id = C.Id 
WHERE C.Name = 'FXRates' 
          AND C.Model_Key = 25
          AND FX.version = 2
          AND FX.effective_dt = 
                (SELECT MAX(effective_dt) FROM aps.v_m_fxrates AS FX2
                 WHERE FX2.currency_code = FX.currency_code)

Answer 3

select 
    c.model_key, v.id,v.category_Id, v.Numeric1,
    c.Name, fx.Currency_code, fx.Rate, fx.effective_dt 
from 
    aps.v_m_fxrates fx 
join 
    aps.t_m_value v on fx.Currency_code = v.Text1 
join 
   aps.t_m_category c on v.Category_Id = c.Id 
where 
   c.Name = 'FXRates' 
   and c.Model_Key = 25 
   and v.Text1 = fx.Currency_code 
   and fx.version = 2 
   and fx.effective_dt = (select MAX(effective_dt) from aps.v_m_fxrates)

试试这个;您使用了fx.effective_dt in，但您必须使用=，因为您需要最大日期记录。使用=后，它只会返回一行。

如何使用日期列过滤数据？

3 个答案: