Given the VB.net code, combine multiple queries into 1 - sql

Question

Given this code below which returns a first recordset (rs) based on a date range with some values that are then used in the second recordset (rs2) to sum up a cost. Further explanation is below the code:
strSQL = "SELECT job, suffix, isnull(qty_scrapped,0),isnull(qty_released,0), isnull(price,0),co_num FROM vwDashboardsQuality "
strSQL &= " WHERE trans_date >= '" & dtpStartDate.Value & "' AND trans_date <= '" & dtpEndDate.Value & "' "
rs = conn.Execute(strSQL)
While Not rs.EOF
strCONUM = Trim("" & rs("co_num").Value)
strSelectString = "SELECT ISNULL(a_cost,0) FROM jobmatl WHERE job='" & rs("job").Value & "' AND suffix = " & Format(rs("suffix").Value)
rs2 = conn.Execute(strSelectString)
While Not rs2.EOF
dblSumActualMaterialCost = dblSumActualMaterialCost + CDbl(rs2(0).Value)
rs2.MoveNext()
End While
rs2.Close()
rs2 = Nothing
rs.MoveNext()
End While
rs.Close()
rs = Nothing
I want to combine the queries into a single query so I am not hitting the database through the second recordset (rs2) just to sum up something that I know can be done in a single query.
Any tips would be helpful. Thank you in advance.

Answer 1

It looks like you're just needing to do an inner join on the two queries to get one result set.
See if this works. If so, you can eliminate the second query and second inner loop.
strSQL = "SELECT d.job, d.suffix, isnull(d.qty_scrapped,0), isnull(d.qty_released,0)," _
& " isnull(d.price,0), d.co_num, ISNULL(m.a_cost,0)" _
& " FROM vwDashboardsQuality d" _
& " INNER JOIN jobmatl m" _
& " ON d.job = m.job" _
& " AND d.suffix = m.suffix" _
& " WHERE trans_date >= '" & dtpStartDate.Value & "'" _
& " AND trans_date <= '" & dtpEndDate.Value & "'"
You can paste this in Management Studio, replacing dates as applicable to check the results.
SELECT d.job, d.suffix, isnull(d.qty_scrapped,0), isnull(d.qty_released,0), isnull(d.price,0), d.co_num,
ISNULL(m.a_cost,0)
FROM vwDashboardsQuality d
INNER JOIN jobmatl m
ON d.job = m.job
AND d.suffix = m.suffix
WHERE trans_date >= '2015-09-29'
AND trans_date <= '2015-09-30'

Answer 2

From your code I see that you are at the end just running a SUM on all values for jobmatl.a_cost that fulfill a condition set by the where clause. So why not doing everything on the same query? And you will save yourself all the unnecessary iterations on the result set, you are loosing previous CPU time and resources there.
Also, you are not using all other values on the first query, why getting them on the first place? I removed them from the following query.
SELECT SUM(j.a_cost)
FROM vwDashboardsQuality vDQ
INNER JOIN jobmatl j
ON vDQ.job = j.job
AND vDQ.suffix = j.suffix
WHERE vDQ.trans_date >= #startdate
AND vDQ.trans_date <= #enddate;