February 28, 2008 at 11:11 am
Hi,ALL
My name is Jeff and I have a puzzling problem with a very simple program.
Groundwork... Visual Studio 2005 Pro using as a Language / Visual Basic 2005
Winforms .net 2.0 SQL Express SP2 / SQL .mdf Database File Used.
I am trying to build my dad a program to calculate and log his mileage on
his 2 Cars. SQL Database Record Number (Key Indexed), DATE, Miles_Start,
Miles_Stop, Total_Miles, Gallons_FillUp, & MPG (In a DataGrid). The Equasion
is simple: Miles_Stop - Miles_Start = Miles_Total / Gallons_FillUp = MPG. I
think(I know why does he... :)) everything goes fine with the miles_stop
minus the miles_start = Miles_Total that works fine and correctly puts the
Miles_Total in and when I change either the Miles_Stop or the Miles_Start
the Miles_Total Changes (OK So Far) But in the SQL Query Box Running the
Query Results in A NULL in the MPG Column! Also reflected in the built
Program No MPG Computation. Also when Running the Query in the Query
Builder the Query Makes another Column (MPG1) Below is What I have
Entered in the Query Builder Box. :w00t: HELP! jrlvid@hughes.net
Thanks in Advance... 🙂
Jeff Link AS., B.S.
SELECT [Record Number], Date, Car, Gallons_FillUp, Miles_Start, Miles_Stop, MPG, Miles_Stop - Miles_Start AS Miles_Total, Miles_Total / Gallons_FillUp AS MPG
FROM Sheet1_Table
February 28, 2008 at 2:40 pm
When you select all raw data in your table, do you have any null values in either Miles_Total or Gallons_FillUp fields? if so, remember that NULL values propagate. IOW, NULL + anything = NULL. To prevent this, look up the ISNULL function to get rid of NULL values in computations.
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