Difference within a field between records

Hi:

Is this as hard as it seems?

Table:

weekID     tankID     Mass
1          1          150
2          1          250
  

Calculate the increase in mass in tank 1 over the week (in this case 250 - 150 = 100). Call this production. Production will be reported. Weekly production over the previous n years will be used as input for statistical analysis.

Thanks

JE Received on Sun Jan 20 2002 - 13:54:41 CST