Same results are getting updated in all rows by using where clause in SQL Server

Question

I'm running a stored procedure inside a foreach loop in c#. After completion, all the rows of a column are getting updated with the top most value. Below is the stored procedure:

ALTER PROCEDURE [dbo].[getservername8]
    @number varchar(255)
AS
    DECLARE @server_name varchar(500)

    SELECT @server_name = short_description 
    FROM [Event_alerts].[dbo].[event_alerts]

    DECLARE @s AS varchar(50)

    SELECT @s = SUBSTRING(@server_name, CHARINDEX('-', @server_name) + 15, 50)

    UPDATE event_alerts 
    SET server_name = @s 
    WHERE number = @number

This is the C# code:

using (SqlCommand command2 = new SqlCommand("getservername8", conn))
{
    command2.CommandType = CommandType.StoredProcedure;

    command2.Parameters.AddWithValue("@number",number);
    command2.Parameters["@number"].Direction = ParameterDirection.Input;

    command2.ExecuteNonQuery();
}

Any help would be much appreciated

Answer 1

The culprit is because you are getting the same value of @server_name for each call. So @s si also same for all. that is why you are inserting the same value in the column

select  @server_name = short_description from [Event_alerts].[dbo].[event_alerts]
declare @s as varchar(50)
select @s= SUBSTRING(@server_name, CHARINDEX('-', @server_name) + 15, 50)

Answer 2

Your code has a valid where clause, so it should only be updating the matching rows. I can only speculate that all rows have the same value for number .

However, you seem to have an error in the definition of @server_name -- and that might be the problem you are referring to. There is no where clause so it is set to an arbitrary value -- possibly from what you would call "the last row". Although that nomenclature is a misinterpretation of what happens.

Your SP is too complex anyway. I suspect that you intend:

alter procedure [dbo].[getservername8] (
    @number varchar(255)
) as
begin
    update ea
        set server_name = substring(short_description, charindex('-', short_description) + 15, 50)
        from event_alerts ea 
        where number = @number;
end;  -- getservername8

Also note the good programming practices:

• The statements end in a semicolon.
• The body of the SP uses begin / end .
• The end is tagged with the name of the SP.