Comparisons in C# and inserting to database

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Hello,

I am trying to insert value (X) to a database, but now i want to compare that,
if X last value is not equal to X present value then INSERT to a database table.
I really dont know what will be its syntax. Thanks

Posted 30-Jan-13 18:18pm

ontheline89

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Naveen.Sanagasetti 31-Jan-13 0:19am

hmmmmm, Could you please elaborate your question...

ontheline89 31-Jan-13 0:22am

i am trying to save values coming from COM Port to a database. when i store these value (X) then many time its value do not change and give same values but after some time its values are changed. I just want to insert the different values in a database.

_Maxxx_ 31-Jan-13 0:26am

Do you really mean you are inserting X - or are you updating a row with a new value of X.
If you are inserting a new row, do you mean you only want to insert the new row if the value of X is not equal to the previous row's X value? If so, what do you mean by 'previous row'? Is it the last row inserted by this user, by any user , with the next lowest key value?
explain more and I am sure someone can give you some SQL to point you in the right direction!

ontheline89 31-Jan-13 0:29am

Yes i am inserting new rows when i get a value of X variable from COM port.
I need to save X to a new row only when its value change from the previous row value.

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Santhosh Kumar Jayaraman · Accepted Answer · 2013-01-30T18:46:00

Using SQL

SQL

Create proc asp_savetable
(@newValue varchar(10)
@id int)
as
BEGIN
   Declare @oldvalue varchar(10)
   Select @oldvalue =name from table1 where id=@id
   If @oldvalue<>@newvalue
      insert into table1 values (@id,@newvalue)
END

here Id,name are two columns in my table table1

Using c#

  using (SqlConnection conn = new SqlConnection(connString))
    {
		string oldvalue="";
		SqlCommand cmd=new SqlCommand("Select name from employee where id=@id",conn)
		cmd.Parameters.Add("@id", SqlDbType.Int);
		cmd.Parameters["@id"].Value = empid;
        	try
        	{
            		conn.Open();
            		oldvalue= cmd.ExecuteScalar().ToString();
        	}
       		 catch (Exception ex)
       		 {
            		Console.WriteLine(ex.Message);
        	}
	}

If (oldvalue!=newvalue)
{
	  using (SqlConnection conn = new SqlConnection(connString))
    {
		string oldvalue="";
		SqlCommand cmd=new SqlCommand("insert into employee values(@id,@name)",conn)
		cmd.Parameters.Add("@id", SqlDbType.Int);
		cmd.Parameters["@id"].Value = empid;
		cmd.Parameters.Add("@name", SqlDbType.VarChar);
		cmd.Parameters["@name"].Value = newvalue;
        	try
        	{
            		conn.Open();
            		cmd.NonExecuteQuery();
        	}
       		 catch (Exception ex)
       		 {
            		Console.WriteLine(ex.Message);
        	}
	}	
}

_Maxxx_ · Accepted Answer · 2013-01-30T18:58:00

It sounds by your comments like you are a novice - so please fogive me if this isn't the case:

In your C# code you probably have some code that does the following

Get X From COM port

Write X to database table

So, you need a field in your class to store the 'old' value of X.

C#

private int oldX = -1;

I initialise it with -1 on teh assumption that it is not possible to receive -1 from the COM port...

Now your code can change to...

C#

Get X from COM PORT

if (X != oldX)
{
    oldX = X;
    write X to database table
}

Comparisons in C# and inserting to database

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