插入数据时检查数据库中是否存在查询 [英] querry for when inserting data check it is exist or not in databse

问题描述

当我通过数据库中的文本框插入数据时.我想检查表中是否已经存在数据，只是显示一条消息数据已存在".
在表中，只有两列id和documentname.
我正在使用sql server和vs2005.
请给我一个酒杯.


在此先感谢

Hi, when i am inserting a data through text box in database. i want to check if data is already exist in the table just shows a message "Data is already exist".
In table there is only two columns id and documentname.
I am using sql server and vs 2005.
Please give me a querry for that.


Thanks in Advance

推荐答案

SELECT * FROM TABLENAME WHERE FIELDNAME = '" + YOURSEARCHSTRING + "';

从此查询获取数据到datatable和

Get the data from this query to datatable and

if(MYDATATABLE.Rows.Count > 0)
{
    Messagebox.Show("Record Already Exists");
}else
{
    //Fire your insert query
}

希望您能从中得到启发.

Hope you will get an idea through this.

Hai fried，
1.最好的方法是在数据库中创建唯一键，并跟踪错误代码以显示错误.
2.另一种方法

Hai fried,
1.The best method is create a unique key in database, and track the error code for displaying error.
2.Another method

IF EXISTS(SELECT   * FROM  tablename WHERE condition )
	BEGIN
		RAISERROR ('already entered',11,1)
	END
	ELSE
	BEGIN
	--		Insert query
	END

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