T-SQL 2008 中的 Unpivot 与 Union 查询

Question

我从中检索数据的数据库的表结构如下

表：ClientSales

ClientSalesId                 int identity (1, 1) (PK)
ClientId                      int (FK)
TermId                        int (FK)
StudentType1Population        int
StudentType1Adjustment        int
StudentType1Sales             int
StudentType1SalesAdjustment   int
StudentType2Population        int
StudentType2Adjustment        int
StudentType2Sales             int
StudentType2SalesAdjustment   int
StudentType3Population        int
StudentType3Adjustment        int
StudentType3Sales             int
StudentType3SalesAdjustment   int
StudentType4Population        int
StudentType4Adjustment        int
StudentType4Sales             int
StudentType4SalesAdjustment   int
StudentType5Population        int
StudentType5Adjustment        int
StudentType5Sales             int
StudentType5SalesAdjustment   int

我必须在报告中显示它，如下所示

对于 ClientId = 1 和 Term Id = 1

                Population   PopulationAdjustment  Sales  SalesAdjustment
StudentType1    313          18                    123    22
StudentType2    233          14                    156    33
StudentType3    234          12                    112    41
StudentType4    233          13                    198    29
StudentType5    343          10                    134    36

我可以通过两种方式执行此操作

SELECT
       'StudentType1'              as DemographicType
       StudentType1Population      as Population,
       StudentType1Adjustment      as PopulationAdjustment,
       StudentType1Sales           as Sales,
       StudentType1SalesAdjustment as SalesAdjustment,
FROM ClientSales
WHERE 1=1
       AND ClientId = 1
       AND TermId = 1

UNION

SELECT
       'StudentType2'              as DemographicType
       StudentType2Population      as Population,
       StudentType2Adjustment      as PopulationAdjustment,
       StudentType2Sales           as Sales,
       StudentType2SalesAdjustment as SalesAdjustment,
FROM ClientSales
WHERE 1=1
       AND ClientId = 1
       AND TermId = 1

-- yada yada yada for the rest of the types...........

或

SELECT
       ClientId,
       Population
FROM
(
       SELECT
              ClientId,
              StudentType1Population,
              StudentType2Population,
              StudentType3Population,
              StudentType4Population,
              StudentType5Population
       FROM ClientSales
) PVTPopulation
UNPIVOT
(
       Population for StudentType IN
       (
              StudentType1Population,
              StudentType2Population,
              StudentType3Population,
              StudentType4Population,
              StudentType5Population
       )
) as UnPvtPopulation

INNER JOIN

(
       SELECT
              ClientId,
              StudentType1PopulationAdjustment,
              StudentType2PopulationAdjustment,
              StudentType3PopulationAdjustment,
              StudentType4PopulationAdjustment,
              StudentType5PopulationAdjustment
       FROM ClientSales
) PVTPopulation
UNPIVOT
(
       PopulationAdjustment for StudentType IN
       (
              StudentType1PopulationAdjustment,
              StudentType2PopulationAdjustment,
              StudentType3PopulationAdjustment,
              StudentType4PopulationAdjustment,
              StudentType5PopulationAdjustment
       )
) as UnPvtPopulationAdjustment

       ON UnPvtPopulationAdjustment.ClientSalesId = UnPvtPopulation.ClientSalesId
       AND REPLACE (UnPvtPopulationAdjustment.StudentType, 'PopulationAdjustment', '') = REPLACE (UnPvtPopulation.StudentType, 'Population', '')

INNER JOIN

(
       SELECT
              ClientId,
              StudentType1Sales,
              StudentType2Sales,
              StudentType3Sales,
              StudentType4Sales,
              StudentType5Sales
       FROM ClientSales
) PVTSales
UNPIVOT
(
       Sales for StudentType IN
       (
              StudentType1Sales,
              StudentType2Sales,
              StudentType3Sales,
              StudentType4Sales,
              StudentType5Sales
       )
) as UnPvtSales

       ON UnPvtSales.ClientSalesId = UnPvtPopulation.ClientSalesId
       AND REPLACE (UnPvtSales.StudentType, 'Sales', '') = REPLACE (UnPvtPopulation.StudentType, 'Population', '')

所以这里有问题：

• 作为最佳实践，我应该使用 UNPIVOT 还是 UNION
• 有没有更好的方法来编写这个 UNPIVOT？

Answer 1

我发现 UNPIVOT 就像一个 where 子句..您可以根据需要使用任意多个

SELECT Col1, Col2, Unp1, Unp2, Unp3
FROM TBL
UNPIVOT (XX For Unp1 (ColXX1, ColXX2))
UNPIVOT (YY For Unp2 (ColYY1, ColYY2))
UNPIVOT (ZZ For Unp2 (ColZZ1, ColZZ2))