SQL Server插入如果不存在
我想在我的表中插入数据，但只插入不存在于我的数据库！
这里是我的代码：
ALTER PROCEDURE [dbo].[EmailsRecebidosInsert] (@_DE nvarchar(50), @_ASSUNTO nvarchar(50), @_DATA nvarchar(30) ) AS BEGIN INSERT INTO EmailsRecebidos (De, Assunto, Data) VALUES (@_DE, @_ASSUNTO, @_DATA) WHERE NOT EXISTS ( SELECT * FROM EmailsRecebidos WHERE De = @_DE AND Assunto = @_ASSUNTO AND Data = @_DATA); END 而错误是：
消息156，级别15，状态1，过程EmailsRecebidosInsert，行11
关键字'WHERE'附近的语法不正确。
而不是下面的代码
BEGIN INSERT INTO EmailsRecebidos (De, Assunto, Data) VALUES (@_DE, @_ASSUNTO, @_DATA) WHERE NOT EXISTS ( SELECT * FROM EmailsRecebidos WHERE De = @_DE AND Assunto = @_ASSUNTO AND Data = @_DATA); END
用。。。来代替
BEGIN IF NOT EXISTS (SELECT * FROM EmailsRecebidos WHERE De = @_DE AND Assunto = @_ASSUNTO AND Data = @_DATA) BEGIN INSERT INTO EmailsRecebidos (De, Assunto, Data) VALUES (@_DE, @_ASSUNTO, @_DATA) END END
更新:(感谢@Marc Durdin指点）
请注意，在高负载下，这有时会失败，因为第二个连接可以在第一个连接执行INSERT之前通过IF NOT EXISTStesting，即竞争条件。 请参阅stackoverflow.com/a/3791506/1836776以获得一个很好的答案，为什么即使在交易中包装也不能解决这个问题。
对于那些寻找最快的方法 ，我最近遇到这些基准 ，显然使用“INSERT SELECT … EXCEPT SELECT …”竟然是最快的5000万条logging或更多。
这里有一些来自文章的示例代码（第三代码块是最快的）：
INSERT INTO #table1 (Id, guidd, TimeAdded, ExtraData) SELECT Id, guidd, TimeAdded, ExtraData FROM #table2 WHERE NOT EXISTS (Select Id, guidd From #table1 WHERE #table1.id = #table2.id) ----------------------------------- MERGE #table1 as [Target] USING (select Id, guidd, TimeAdded, ExtraData from #table2) as [Source] (id, guidd, TimeAdded, ExtraData) on [Target].id =[Source].id WHEN NOT MATCHED THEN INSERT (id, guidd, TimeAdded, ExtraData) VALUES ([Source].id, [Source].guidd, [Source].TimeAdded, [Source].ExtraData); ------------------------------ INSERT INTO #table1 (id, guidd, TimeAdded, ExtraData) SELECT id, guidd, TimeAdded, ExtraData from #table2 EXCEPT SELECT id, guidd, TimeAdded, ExtraData from #table1 ------------------------------ INSERT INTO #table1 (id, guidd, TimeAdded, ExtraData) SELECT #table2.id, #table2.guidd, #table2.TimeAdded, #table2.ExtraData FROM #table2 LEFT JOIN #table1 on #table1.id = #table2.id WHERE #table1.id is null
我会用一个合并：
create PROCEDURE [dbo].[EmailsRecebidosInsert] (@_DE nvarchar(50), @_ASSUNTO nvarchar(50), @_DATA nvarchar(30) ) AS BEGIN with data as (select @_DE as de, @_ASSUNTO as assunto, @_DATA as data) merge EmailsRecebidos t using data s on s.de = t.de and s.assunte = t.assunto and s.data = t.data when not matched by target then insert (de, assunto, data) values (s.de, s.assunto, s.data); END
尝试下面的代码
ALTER PROCEDURE [dbo].[EmailsRecebidosInsert] (@_DE nvarchar(50), @_ASSUNTO nvarchar(50), @_DATA nvarchar(30) ) AS BEGIN INSERT INTO EmailsRecebidos (De, Assunto, Data) select @_DE, @_ASSUNTO, @_DATA EXCEPT SELECT De, Assunto, Data from EmailsRecebidos END
INSERT命令没有WHERE子句 – 你必须这样写：
ALTER PROCEDURE [dbo].[EmailsRecebidosInsert] (@_DE nvarchar(50), @_ASSUNTO nvarchar(50), @_DATA nvarchar(30) ) AS BEGIN IF NOT EXISTS (SELECT * FROM EmailsRecebidos WHERE De = @_DE AND Assunto = @_ASSUNTO AND Data = @_DATA) BEGIN INSERT INTO EmailsRecebidos (De, Assunto, Data) VALUES (@_DE, @_ASSUNTO, @_DATA) END END
除了IF EXISTS之外，根据您的SQL Server版本（2012？），还可以使用MERGE，如下所示：
ALTER PROCEDURE [dbo].[EmailsRecebidosInsert] ( @_DE nvarchar(50) , @_ASSUNTO nvarchar(50) , @_DATA nvarchar(30)) AS BEGIN MERGE [dbo].[EmailsRecebidos] [Target] USING (VALUES (@_DE, @_ASSUNTO, @_DATA)) [Source]([De], [Assunto], [Data]) ON [Target].[De] = [Source].[De] AND [Target].[Assunto] = [Source].[Assunto] AND [Target].[Data] = [Source].[Data] WHEN NOT MATCHED THEN INSERT ([De], [Assunto], [Data]) VALUES ([Source].[De], [Source].[Assunto], [Source].[Data]); END
我做了与SQL SERVER 2012相同的事情，它的工作
Insert into #table1 With (ROWLOCK) (Id, studentId, name) SELECT '18769', '2', 'Alex' WHERE not exists (select * from #table1 where Id = '18769' and studentId = '2')
