what code should be written so that same code should not be inserted

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what code should be written so that same data should not be inserted again in database.

Posted 28-Apr-13 9:42am

priti mishra

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CHill60 28-Apr-13 15:44pm

This question is not clear. Use the Improve question link to add more detail - for example the line(s) of code that you are using to insert data into the database

PIEBALDconsult 28-Apr-13 16:22pm

You probably want to look into "referential integrity", "unique index", and "primary key".

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DaveAuld · Answer 1 · 2013-04-28T10:42:00

There are different approaches depending on what you are trying to do;

1) Mark the database schema such that fields must be unique, are primary keys etc.

2) Build a hash from the data and store that with the data as a field. When you create a new record calculate the hash and try and save the new data. The hash field must be marked unique.

3) Come up with your own method of checking for uniqueness.

Thanks7872 · Answer 2 · 2013-04-28T18:08:00

Suppose your database contains field called username,then you can check if username exist in the database or not,if not then enter the details else throw an exception.Example is given below.

C#

SqlConnection conn = new SqlConnection();
 conn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["connection string name"].ConnectionString;
 conn.Open();
 String user=TextBox1.Text;
 SqlCommand check = new SqlCommand("select * from table_name where name=@user", conn);
 cmd.Parameters.Add(new SqlParameter("@user",user));
 SqlDataReader reader = check.ExecuteReader();
 if (!reader.Read())
 {
        /*Insert details into database*/
 }
 else
 {
       /*Throw en Exception*/
 }

what code should be written so that same code should not be inserted

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