比较和合并来自2个具有相同结构的表的数据

Question

有两个具有相同结构的表，如SQLFiddle，是否可以构建一个SQL语句来比较两个表的列的值（其中id是唯一键），并在格式返回变更列的列表：

columnname, oldvalue, newvalue 

凡oldvalue是Table1和newvalue值在Table2值。

Answer 1

你可以做这样的事情：

SELECT T1.Id 
     ,'Name' AS ColumnName 
     ,CAST(T1.name AS VARCHAR(MAX)) AS OldValue 
     ,CAST(T2.name AS VARCHAR(MAX)) AS NewValue 
FROM Table1 AS T1 
FULL OUTER JOIN Table2 AS T2 
    ON T1.id = T2.id 
UNION 
SELECT T1.Id 
     ,'Amount' 
     ,CAST(T1.amount AS VARCHAR(MAX)) 
     ,CAST(T2.amount AS VARCHAR(MAX)) 
FROM Table1 AS T1 
FULL OUTER JOIN Table2 AS T2 
    ON T1.id = T2.id 

Answer 2

您需要使用MERGE语句，请注意它只能从SQL 2008年起

这里有一个例子

MERGE Production.ProductInventory AS target 
USING (SELECT ProductID, SUM(OrderQty) FROM Sales.SalesOrderDetail AS sod 
    JOIN Sales.SalesOrderHeader AS soh 
    ON sod.SalesOrderID = soh.SalesOrderID 
    AND soh.OrderDate = @OrderDate 
    GROUP BY ProductID) AS source (ProductID, OrderQty) 
ON (target.ProductID = source.ProductID) 
WHEN MATCHED AND target.Quantity - source.OrderQty <= 0 
    THEN DELETE 
WHEN MATCHED 
    THEN UPDATE SET target.Quantity = target.Quantity - source.OrderQty, 
        target.ModifiedDate = GETDATE() 
OUTPUT $action, Inserted.ProductID, Inserted.Quantity, Inserted.ModifiedDate, Deleted.ProductID, 
    Deleted.Quantity, Deleted.ModifiedDate; 
GO 

你可以在这里了解更多关于合并的信息SQL merge

Answer 3

如果您只想要有差异的行：

SELECT COALESCE(T1.Id, T2.Id) Id 
     ,'Name' AS ColumnName 
     ,CAST(T1.name AS VARCHAR(MAX)) AS OldValue 
     ,CAST(T2.name AS VARCHAR(MAX)) AS NewValue 
FROM Table1 AS T1 
FULL OUTER JOIN Table2 AS T2 
    ON T1.id = T2.id 
WHERE COALESCE(T1.name,'**') != COALESCE(T2.name ,'**') 
UNION ALL 
SELECT COALESCE(T1.Id, T2.Id) Id 
     ,'Amount' AS ColumnName 
     ,CAST(T1.Amount AS VARCHAR(MAX)) AS OldValue 
     ,CAST(T2.Amount AS VARCHAR(MAX)) AS NewValue 
FROM Table1 AS T1 
FULL OUTER JOIN Table2 AS T2 
    ON T1.id = T2.id 
WHERE COALESCE(T1.Amount,0) != COALESCE(T2.Amount,0)