我插入时如何检查数据库中是否已经存在的数据 [英] how to check data it is already exists or not in database when i am inserting

问题描述

您好，我制作了一个Web应用程序，当我从文本框中向表中插入数据时，我想检查数据是否已存在.如果数据已存在，则我希望消息数据已存在"是什么类型我应该写的查询内容?

或如何使用不存在的查询?

我正在使用sql server.

在此先感谢

Hi, i made a web application and when i insert a data from text box to table i want to check data is already exist or not .if data is already exist then i want a message "data is already exists" what type of query i should wrote ?

or how to use not exists query ?

i am using sql server.

Thanks in advance

推荐答案

创建类似于以下&检查返回值并相应显示消息..

Create proc similar to the following & check the return value and show the message accordingly..

Create Procedure Proc_Name
(
    @EMailAdress varchar(50) = null,
}
AS

IF EXISTS (SELECT UserID  FROM E-MAIL WHERE EMailAdress = @EMailAdress)
BEGIN
    return 0
END
ELSE
BEGIN
    INSERT INTO E-MAIL (UserID,EMailAdress,Description) VALUES (UserID,@EMailAdress,@Description)
    return 1
END

在代码中，检查返回值，例如...

In the code, check for the return value something like...

int returnValue =  (int) comm.ExecuteScalar();

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