如何检查数据库中是否存在值， [英] How to check if value exists in database,

问题描述

大家好，

我在Windows窗体中有一个文本框.我的问题是，如何检查通过数据库在文本框中输入的现有文本?请举一个例子.

Hi all,

I have a text box in a windows form. My question is, how to check existing text which is entered in text box through database? Please reply me with an example.

推荐答案

在SQL Server中创建存储过程，例如:

Hi,
Make a stored procedure in SQL Server for example:

Create	Procedure	FindString(<br />
@MyString	nvarchar(50))<br />
As<br />
Begin<br />
		Select	*	From	MyTable<br />
					Where		Value = @MyString<br />
End

在.NET中创建类，例如:

Make a Class in .NET For example :

public class ReadData
{
    public bool FindString(string myString)
    {
        SqlConnection connection = new SqlConnection();
        connection.ConnectionString = "Server=..."; //Your connection string
        SqlCommand command = new SqlCommand();
        command.Connection = connection;
        command.CommandType = CommandType.StoredProcedure;
        command.CommandText = "FindString";
        command.Parameters.AddWithValue("@MyString", myString);
        try
        {
            connection.Open();
            SqlDataReader reader = command.ExecuteReader();
            while (reader.Read())
            {
                return true;
            }
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
        finally
        {
            if (connection.State == ConnectionState.Open)
                connection.Close();
        }                
        return false;
    }
}

使用该类.例如:

Use the class. for example :

ReadData r = new ReadData();

if (r.FindString("Shahingg"))
    MessageBox.Show("I Found it!");
else
    MessageBox.Show("I can't Find it!");

不要忘记，您的Class需要以下名称空间:

Do not forget that you need below namespaces for your Class :

using System.Data.SqlClient;
using System.Data;

祝你好运

Good Luck

CREATE PROCEDURE Procedure_Name
@mystring varchar(100),
@isExist bit out
AS
BEGIN
	if exists(select column1 from tblTable1 where column1=@mystring)
	begin
	select @isExist=1
	end
	else
	begin
	select @isExist=0
	end
	
	
END
GO

然后编写方法以检查该值是否存在
那就是@ isExist = 1表示该值存在.否则不存在.
希望这会对您有所帮助.

then write the method to check whether the value exist or not
thatis if @isExist=1 that means the value exist.otherwise not..
Hope this may help you..

If(exists(select * from table where column=@clounm))
Begin
Selct ''true''
END
ELSE
BEGIN
select ''false''
END

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