SQL Server 2005在列中划分两行

Question

I have a table set up like this:

        Description                Jan |  Feb  | Mar  | Apr .....   
Volume        

Days in Month

Gal/Day Average

I would like to be able to divide the volume for each month by the Days (and multiply by 100) to fill in the gal/day average row for each month.

The farthest I've gotten code wise is:

Update Table
set [Jan] = ?
where Description = 'Gal/Day Average'

Answer 1

Not a very good data format, but you could do:

Update toupdate
    set [Jan] = volume.jan / dim.jan
    from table toupdate cross join 
         table volume cross join
         table dim
    where toupdate.description = 'Gal/Day Average' and
          volume.description = 'Volume' and
          dim.description = 'Days In Month';

A much better data format would have the columns:

• month
• (possibly year)
• volume
• daysinmonth
• average