Question

这个查询有效，但看起来非常低效。必须有更好的方法吗？

我要做的是根据公司所在的区域从MarketRates表中选择4个不同的列。只有4个区域，在Company表中存储为整数1-4。因此，例如，如果区域为“1”，那么我想选择4个南加州列（列名称为SCA *），但如果区域为“2”，那么我想选择4个Norhtern California列（列名是NCA *）等。

我知道表格应该以不同的方式构建，但这是我必须处理的。

MarketRates表包含这些列（SCA =南加州，NCA =北加州，SNV =南内华达州，NAZ =北亚利桑那州：

EndingDate - date
SCA_MRK - 十进制（8,2）
SCA_RATE - decimal（8,2）
SCA_COMP - 小数（8,2）
SCA_NEG - 小数（8,2）
NCA_MRK - 小数（8,2）
NCA_RATE - decimal（8,2）
NCA_COMP - 小数（8,2）
NCA_NEG - 小数（8,2）
SNV_MRK - 十进制（8,2）
SNV_RATE - decimal（8,2）
SNV_COMP - decimal（8,2）
SNV_NEG - 十进制（8,2）
NAZ_MRK - 十进制（8,2）
NAZ_RATE - 小数（8,2）
NAZ_COMP - 小数（8,2）
NAZ_NEG - 小数（8,2）

这是我正在使用的当前查询：

Select CompanyName
  , case TerritoryNumber 
    when 1 then (Select top 1 coalesce(SCA_MRK,0) From MarketRates Order by EndingDate desc) 
    when 2 then (Select top 1 coalesce(NCA_MRK,0) From MarketRates Order by EndingDate desc) 
    when 3 then (Select top 1 coalesce(SNV_MRK,0) From MarketRates Order by EndingDate desc) 
    when 4 then (Select top 1 coalesce(NAZ_MRK,0) From MarketRates Order by EndingDate desc) 
  end AS MRK
  , case TerritoryNumber 
    when 1 then (Select top 1 coalesce(SCA_RATE,0) From MarketRates Order by EndingDate desc) 
    when 2 then (Select top 1 coalesce(NCA_RATE,0) From MarketRates Order by EndingDate desc) 
    when 3 then (Select top 1 coalesce(SNV_RATE,0) From MarketRates Order by EndingDate desc) 
    when 4 then (Select top 1 coalesce(NAZ_RATE,0) From MarketRates Order by EndingDate desc) 
  end AS RATE
  , case TerritoryNumber 
    when 1 then (Select top 1 coalesce(SCA_COMP,0) From MarketRates Order by EndingDate desc) 
    when 2 then (Select top 1 coalesce(NCA_COMP,0) From MarketRates Order by EndingDate desc) 
    when 3 then (Select top 1 coalesce(SNV_COMP,0) From MarketRates Order by EndingDate desc) 
    when 4 then (Select top 1 coalesce(NAZ_COMP,0) From MarketRates Order by EndingDate desc) 
  end AS COMP
  , case TerritoryNumber 
    when 1 then (Select top 1 coalesce(SCA_NEG,0) From MarketRates Order by EndingDate desc) 
    when 2 then (Select top 1 coalesce(NCA_NEG,0) From MarketRates Order by EndingDate desc) 
    when 3 then (Select top 1 coalesce(SNV_NEG,0) From MarketRates Order by EndingDate desc) 
    when 4 then (Select top 1 coalesce(NAZ_NEG,0) From MarketRates Order by EndingDate desc) 
  end AS NEG
from Company 
where CompanyID = 'THISID'

Answer 1

您只需从MarketRates中选择一行，因为您每次都引用同一行。在子查询中选择它并加入它，您可以在整个查询中引用它。我重写了MRK的样子，其他列也有类似的语法/逻辑。

Select CompanyName
  , case TerritoryNumber 
    when 1 then coalesce(SCA_MRK,0)
    when 2 then coalesce(NCA_MRK,0)
    when 3 then coalesce(SNV_MRK,0)
    when 4 then coalesce(NAZ_MRK,0)
  end AS MRK
  , ...etc
from Company 
cross join (select top 1 * from MarketRates order by EndingDate desc) MarketRates
where CompanyID = 'THISID'

Answer 2

DECLARE 
    @TerritoryID INT,
    @CompanyName VARCHAR(32);

SELECT 
    @CompanyName = CompanyName,
    @TerritoryID = TerritoryNumber 
FROM Company 
WHERE CompanyID = 'THISID';

SELECT TOP 1
    CompanyName = @CompanyName,
    MRK = CASE @TerritoryID
        WHEN 1 THEN SCA_MRK
        WHEN 2 THEN NCA_MRK
        WHEN 3 THEN SNV_MRK
        WHEN 4 THEN NAZ_MRK END,
    RATE = CASE @TerritoryID
        WHEN 1 THEN SCA_RATE
        WHEN 2 THEN NCA_RATE
        WHEN 3 THEN SNV_RATE
        WHEN 4 THEN NAZ_RATE END,
    COMP = CASE @TerritoryID
        WHEN 1 THEN SCA_COMP
        WHEN 2 THEN NCA_COMP
        WHEN 3 THEN SNV_COMP
        WHEN 4 THEN NAZ_COMP END,
    NEG = CASE @TerritoryID
        WHEN 1 THEN SCA_NEG
        WHEN 2 THEN NCA_NEG
        WHEN 3 THEN SNV_NEG
        WHEN 4 THEN NAZ_NEG END
FROM MarketRates
ORDER BY EndingDate DESC;

Answer 3

您可以使用一个案例块保持清洁和快速。（您可以替换变量类型以匹配列数据类型。）检查下面创建的动态SQL。

DECLARE @CompanyName varchar(50), @TerritoryNum int, @ColumnType varchar(10), @SQL VARCHAR(1000);
SELECT @CompanyName = CompanyName ,@TerritoryNum = TerritoryNumber 
    FROM Company WHERE CompanyID = 'THISID'
SET @ColumnType = CASE @TerritoryNum WHEN 1 THEN 'SCA_'
                                    WHEN 2 THEN 'NCA_'
                                    WHEN 3 THEN 'SNV_'
                                    WHEN 4 THEN 'NAZ_'
                                    END

SET @SQL = '
SELECT 
    ''' + @CompanyName + ''' AS CompanyName,
    COALESCE(' + @ColumnType + 'MRK,0) AS MRK,
    COALESCE(' + @ColumnType + 'RATE,0) AS RATE,
    COALESCE(' + @ColumnType + 'COMP,0) AS COMP,
    COALESCE(' + @ColumnType + 'NEG,0) AS NEG
FROM MarketRates
'
PRINT @SQL
EXEC(@SQL)

动态查询（可以从Print看到）就像下面那样简单，其中Company表在CompanyName列中有'Comp'，在TerritoryNumber列中有2。尝试将其更改为Company表中的其他数字，并在动态查询中显示相应的MarketRates列。

SELECT 
    'Comp' AS CompanyName,
    COALESCE(NCA_MRK,0) AS MRK,
    COALESCE(NCA_RATE,0) AS RATE,
    COALESCE(NCA_COMP,0) AS COMP,
    COALESCE(NCA_NEG,0) AS NEG
FROM MarketRates

必须有更好的方法来编写此查询？

3 个答案: