Search for multiple values in SQL Server as quickly as possible - sql

Question

I have the following sql statement pulling data from a stored view:
foreach (var id in insert_idlist[0])
{
mssql_con.Open();
//top 1 for duplicate removal
//slowdown?
var mssql_select = "SELECT * FROM dbo.export_to_web WHERE SKU = '" + id + "'";
}
I want to rewrite the sql statement to insert all ids into a single query using an IN clause or similar to speed up execution. However I am aware that IN is a relatively slow operation, so I was hoping to get some expert advice on the fastest possible way of retrieving my data.
Speed is my only concern in this question.
Please note that security is not an issue as this application is pulling all it's variables from an internal database with no direct web access.
Updated code:
try
{
//foreach (var id in insert_idlist[0])
//{
mssql_con.Open();
//top 1 for duplicate removal
//slowdown?
//var mssql_select = "SELECT * FROM dbo.export_to_web WHERE SKU = '" + id + "'";
var mssql_select = "SELECT * FROM dbo.export_to_web WHERE SKU IN (" + insert_idlist .Select(x => "'" + x + "'") .Aggregate((x, y) => x + "," + y) + ")";
//var mssql_select = "SELECT * FROM dbo.Book5 WHERE SKU = '"+id+"'";
SqlCommand cmd = new SqlCommand(mssql_select, mssql_con);
cmd.CommandTimeout = 0;
lbl_dev.Text += "teest";
//Create a data reader and Execute the command
try
{
SqlDataReader dataReader = cmd.ExecuteReader();
//Read the data and store them in the list
while (dataReader.Read())
{
insert_idlist[1].Add(dataReader["supplier name"] + " " + dataReader["range description"] + " " + dataReader["item description"]);
insert_idlist[3].Add(dataReader["Sale Price"] + "");
insert_idlist[2].Add(dataReader["WebDesc"] + "");
//insert_idlist[3].Add(dataReader["id"] + "");removed
insert_idlist[4].Add(dataReader["WebDimensions"] + "");
insert_idlist[5].Add(dataReader["RRP"] + "");
insert_idlist[6].Add(dataReader["Normal Price"] + "");
insert_idlist[7].Add("482"); //add me
insert_idlist[8].Add(dataReader["ID"] + "");
lbl_dev.Text += dataReader["supplier name"] + " " + dataReader["range description"] + " " + dataReader["item description"];
lbl_dev.Text += mssql_select;
about_to_insert = about_to_insert + 1;
}
lbl_dyn_status.Text = "Record 0 of " + about_to_insert + "updated.";
dataReader.Close();
mssql_con.Close();
}
catch (Exception e)
{
lbl_dev.Text = "" + e.Message;
}
// }
}
catch (Exception e)
{
lbl_dev.Text = "" + e.Message;
}

Answer 1

I want to rewrite the sql statement to insert all ids into a single
query using an IN clause or similiar.
You can use INSERT INTO ... SELECT ... like so:
INSERT INTO ATable(...)
SELECT * FROM dbo.export_to_web WHERE SKU = someid;
Note that: You have to list the columns' names in the INSERT clause to match what is returned by SELECT *.

Answer 2

If you are on 2008 or higher, the best way to do is pass the values into a Table-Valued Parameter. I always point people to a blog post I wrote here for that.
However, IN is not necessarily a slow operation, as long as the field that you are searching is indexed appropriately - and it would almost certainly be faster than the 'connection per item' approach.
The SQL would then be something like:
var mssql_select = "SELECT * FROM dbo.export_to_web WHERE SKU IN (" + insert_idlist
.Select(x => "'" + x + "'")
.Aggregate((x, y) => x + "," + y) + ")";
Disclaimer - that LINQ may not be 100% spot on :)