Sql server 查找两个表之间的增量

我有两个表，我们称它们为表A和表B。两个表的大小不同，但主键（ID）相同。变量字段为（名称）。我想从表B返回以下行：

数据发生了变化

以前没有数据

每次执行SQL时，返回的数据将有一个附加的列标记为comments，其值设置为高于。我已经在下面编写了T-SQL，但是有更好的方法吗

SELECT [ID]
,[Name]
,'Data did not exist before' AS [Comment]
FROM TABLENAMEB
WHERE [ID] NOT IN (SELECT [ID] FROM #TABLENAMEA)
UNION
SELECT B.[ID]
,B.[Name]
,'Data has changed' AS [Comment]
FROM  TABLENAMEB B
LEFT JOIN TABLENAMEA A ON B.[ID] = A.[ID] 
WHERE A.[Name] != B.[Name]

---

您可能可以使用left join和

case

获得相同的结果：

SELECT [ID]
      ,[Name]
      ,CASE 
       WHEN A.[Name] IS NULL THEN -- Assuming `Name` in table a is not nullable.
           'Data did not exist before'
       WHEN B.[Name] != A.[Name THEN 
           'Data has changed'
       ELSE 
           ''
       END As [Comment]
FROM TABLENAMEB As B
LEFT JOIN #TABLENAMEA As A ON B.[ID] = A.[ID]

---

您可能可以使用left join和

case

获得相同的结果：

SELECT [ID]
      ,[Name]
      ,CASE 
       WHEN A.[Name] IS NULL THEN -- Assuming `Name` in table a is not nullable.
           'Data did not exist before'
       WHEN B.[Name] != A.[Name THEN 
           'Data has changed'
       ELSE 
           ''
       END As [Comment]
FROM TABLENAMEB As B
LEFT JOIN #TABLENAMEA As A ON B.[ID] = A.[ID]

大概是这样的：

DECLARE @tblA TABLE(ID INT, Name VARCHAR(100));
INSERT INTO @tblA VALUES(1,'test1'),(2,'test2'),(4,'test4');

DECLARE @tblB TABLE(ID INT, Name VARCHAR(100));
INSERT INTO @tblB VALUES(2,'test2'),(3,'test3'),(4,'different');

SELECT CASE WHEN A.ID IS NULL THEN 'missing in A'
            WHEN B.ID IS NULL THEN 'missing in B'
            WHEN A.Name<>B.Name THEN 'different'
            ELSE 'okay' END AS Comment
            ,*
FROM @tblA AS A
FULL OUTER JOIN @tblB AS B ON A.ID=B.ID

大概是这样的：

DECLARE @tblA TABLE(ID INT, Name VARCHAR(100));
INSERT INTO @tblA VALUES(1,'test1'),(2,'test2'),(4,'test4');

DECLARE @tblB TABLE(ID INT, Name VARCHAR(100));
INSERT INTO @tblB VALUES(2,'test2'),(3,'test3'),(4,'different');

SELECT CASE WHEN A.ID IS NULL THEN 'missing in A'
            WHEN B.ID IS NULL THEN 'missing in B'
            WHEN A.Name<>B.Name THEN 'different'
            ELSE 'okay' END AS Comment
            ,*
FROM @tblA AS A
FULL OUTER JOIN @tblB AS B ON A.ID=B.ID

---

编辑：我刚刚注意到你正在使用2008。以下功能没有任何用处

您使用的是T-SQL，因此您使用的是SQL Server。查看这两个专门为回答您的问题而设计的功能之一：

更改数据捕获

时态表

---

编辑：我刚刚注意到你正在使用2008。以下功能没有任何用处

您使用的是T-SQL，因此您使用的是SQL Server。查看这两个专门为回答您的问题而设计的功能之一：

更改数据捕获

时态表