根据表

Question

1）表1表示table1，结构为：

moduleID | moduleName 10 | XYZ 20 | PQR 30 | ABC

2）表2说table2结构为：

moduleID | Level | Value 10 | 1 | 20 10 | 2 | 30 30 | 3 | 40 10 | 3 | 50 20 | 2 | 30 moduleID是table1中的主键，列level的值可以是值1到3 现在需要显示如下数据：

moduleID | moduleName | Level1 | Level2 | Level3 10 | XYZ | 20 | 30 | 50 20 | PQR | NULL | 30 | NULL 30 | ABC | NULL | NULL | 50
简而言之，table2中列Level的值显示为Level1，Level2和Level3，并且对应于每个级别的值将填充在相​​应的moduleID行中。 对此有何帮助？在SQL中初学者。与Views有关吗？

Answer 1

您可以使用条件聚合：

select t1.moduleID, t1.moduleName,
       MAX(CASE WHEN Level = 1 THEN Value END) Level1,
       MAX(CASE WHEN Level = 2 THEN Value END) Level2,
       MAX(CASE WHEN Level = 3 THEN Value END) Level3
from table1 as t1
left join table2 as t2 on t1.moduleID = t2.moduleID
group by t1.moduleID, t1.moduleName

Answer 2

为表2中的每个级别执行select t1.*, t2_l1.value as Level1, t2_l2.value as Level2, t2_l3.value as Level3 from table1 t1 left join table2 t2_l1 on t1.moduleID = t2_l1.moduleID and t2_l1.Level = 'Level1' left join table2 t2_l2 on t1.moduleID = t2_l2.moduleID and t2_l2.Level = 'Level2' left join table2 t2_l3 on t1.moduleID = t2_l3.moduleID and t2_l3.Level = 'Level3' 。

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如果moduleID具有多个不同的级别值，则将返回所有这些值。 （如果你想要总和，请看看Giorgos Betsos的回答。）

Answer 3

请参阅此过程，它将适用于您的预期答案。

CREATE TABLE Table1
(moduleName VARCHAR(50),moduleID INT)
GO
--Populate Sample records
INSERT INTO Table1 VALUES('.NET',10)
INSERT INTO Table1 VALUES('Java',20)
INSERT INTO Table1 VALUES('SQL',30)

CREATE TABLE Table2
(moduleID INT,[Level] INT,Value INT)
GO
--Populate Sample records
INSERT INTO Table2 VALUES(10,1,20)
INSERT INTO Table2 VALUES(10,2,30)
INSERT INTO Table2 VALUES(30,3,40)
INSERT INTO Table2 VALUES(10,3,50)
INSERT INTO Table2 VALUES(20,2,30)
INSERT INTO Table2 VALUES(20,4,60)
GO

CREATE VIEW [dbo].[vw_tabledata]
AS
SELECT t1.[moduleID],[moduleName]
      ,[Level]
      ,[Value]
  FROM [db_Sample].[dbo].[Table2] t2 inner join [db_Sample].[dbo].[Table1] t1 on t1.[moduleID] = t2.[moduleID]
GO







DECLARE @DynamicPivotQuery AS NVARCHAR(MAX)
DECLARE @ColumnName AS NVARCHAR(MAX)

--Get distinct values of the PIVOT Column 
SELECT @ColumnName= ISNULL(@ColumnName + ',','') 
       + QUOTENAME([Level])
FROM (SELECT DISTINCT [Level] FROM Table2) AS [Level]

--Prepare the PIVOT query using the dynamic 
SET @DynamicPivotQuery = 
  N'SELECT moduleID,moduleName, ' + @ColumnName + '
    FROM [vw_tabledata] 
    PIVOT(MAX(Value) 
          FOR [Level] IN (' + @ColumnName + ')) AS PVTTable'
--Execute the Dynamic Pivot Query
EXEC sp_executesql @DynamicPivotQuery