when you want to write a search using .net and MSSQL, it’s a pain. This is because you’re forced to select every row in the table and then only display a small subset of it. This works okay for tables that have a few hundred rows, as query caching can make this faster. But what happens when you’re searching a table with half a million rows?
Unless you’re a complete masochist, you’re doing to want to split this into a more manageable data set, otherwise you’re gonna eat all the memory on your server. But this means that you can no longer use the DataSet.Tables[0].Rows.Count property to figure out how many rows you have. You can write a second stored procedure that’ll count the rows. But who wants to clog up their database with tons of stored procedures for no reason? Let’s consolidate it into one.
So what does this look like?
First: the stored procedure.
We’ll use output parameters to pass the row count back to our code
create procedure [dbo].[Search]
@searchText varchar(512), @recordsToReturn INT, @pageNumber INT, @numberofrows INT OUTPUT
AS
-- get the page we want to view
select * from
(
select *, ROW_NUMBER() OVER (ORDER BY creation_timestamp DESC) AS row from [table] where [table].columnName like '%' + @searchText + '%'
)
AS results WHERE row between (@pageNumber - 1) * @recordsToReturn + 1 and @pageNumber*@recordsToReturn;
-- get the total number of rows, not just the subset we want
set @numberofrows = (select count(*) from [table] where [table].columnName like '%' + @searchText + '%')
END
Now the C# (this’ll work in VB too, but feel free to convert it yourself)
SqlConnection conn = new SqlConnection();
conn.ConnectionString = ".....your connection string here.....";
conn.Open();
DataSet returnData = new DataSet();
SqlDataAdapter da = new SqlDataAdapter( "SearchMessages", conn);
da.SelectCommand.CommandType = CommandType.StoredProcedure;
da.SelectCommand.Parameters.Add("@searchText", SqlDbType.VarChar).Value = "bob";
da.SelectCommand.Parameters.Add("@recordsToReturn", SqlDbType.Int).Value = 10;
da.SelectCommand.Parameters.Add("@pageNumber", SqlDbType.Int).Value = 1;
//number of rows
SqlParameter outputParameter = new SqlParameter("@numberofrows", SqlDbType.Int, 2);
outputParameter.Direction = ParameterDirection.Output;
da.SelectCommand.Parameters.Add(outputParameter);
da.Fill(returnData, "theData");
int numberOfRowsInDataSet = (int)outputParameter.Value;
da.Dispose();
conn.Close();
Best of luck! As always, leave a message in the comments if you have questions
Jeremy Massel 