将IF ... ELSE语句添加到存储过程以跳过重复的主键

Question

我在物理C＃代码中尝试捕获，当错误累积时跳过此插入过程并继续循环以填充数据库。然而，这是糟糕的编码实践。

所以我想在下面的存储过程中添加一个IF语句，如果主键已经存在，它将跳过。我的主键是@id。

我该如何解决这个问题？

CREATE PROCEDURE InsertProc
    (
    @id int, 
    @to nvarchar(100), 
    @from nvarchar(100), 
    @subject nvarchar(100), 
    @date datetime
    )
AS
    INSERT INTO Emails_Log (Email_ID, e_To, e_From, e_Subject, e_Date) 
    VALUES (@id, @to, @from, @subject, @date)

Answer 1

CREATE PROCEDURE InsertProc
    (
    @id int, 
    @to nvarchar(100), 
    @from nvarchar(100), 
    @subject nvarchar(100), 
    @date datetime
    )
    AS
    IF NOT EXISTS (SELECT NULL FROM Emails_Log
                    WHERE Email_ID = @ID)
    BEGIN
        INSERT INTO Emails_Log (Email_ID, e_To, e_From, e_Subject, e_Date) 
            VALUES (@id, @to, @from, @subject, @date)
    END

如果您确实想要更新记录（如果已经存在）并插入（如果不存在），则模式如下：

CREATE PROCEDURE InsertProc
    (
       @id int, 
       @to nvarchar(100), 
       @from nvarchar(100), 
       @subject nvarchar(100), 
       @date datetime
    )
    AS
       UPDATE Emails_Log
          SET e_To = @to, 
              e_From = @from, 
              e_Subject = @subject, 
              e_Date = @date
        WHERE Email_ID = @ID
       -- If there was no update it means that @ID does not exist,
       -- So we proceede with insert
       IF @@ROWCOUNT = 0
       BEGIN
          INSERT INTO Emails_Log (Email_ID, e_To, e_From, e_Subject, e_Date) 
               VALUES (@id, @to, @from, @subject, @date)
       END

Answer 2

CREATE PROCEDURE InsertProc
    (
    @id int, 
    @to nvarchar(100), 
    @from nvarchar(100), 
    @subject nvarchar(100), 
    @date datetime
    )
    AS
    IF EXISTS(SELECT * From Emails_Log Where Email_ID = @id)
    UPDATE Emails_Log (Email_ID, e_To, e_From, e_Subject, e_Date) 
            SET e_To = @to, e_From = @from, e_Subject = @subject, e_Date = @date
            WHERE Email_ID = @id
    ELSE
    INSERT INTO Emails_Log (Email_ID, e_To, e_From, e_Subject, e_Date) 
            VALUES (@id, @to, @from, @subject, @date)

另一种方法是使用MERGE命令。

请看this thread on SO to know more。

Answer 3

您可以检查表格中是否存在记录 将记录插入一个陈述中。

Answer 4

试试这段代码

CREATE PROCEDURE InsertProc
(
@id int, 
@to nvarchar(100), 
@from nvarchar(100), 
@subject nvarchar(100), 
@date datetime
)
AS
IF NOT EXISTS (SELECT Email_ID From Emails_Log Where Email_ID = @id)
BEGIN
    INSERT INTO Emails_Log (Email_ID, e_To, e_From, e_Subject, e_Date) 
        VALUES (@id, @to, @from, @subject, @date)
END