Given the following sample data:
tblData
Date Sales
----------------------
2011-12-01 122
2011-12-02 433
2011-12-03 213
...
2011-12-31 235
2011-11-01 122
2011-11-02 433
2011-11-03 213
...
2011-11-30 235
2011-10-10 122
2011-10-11 433
2011-10-12 213
...
2011-10-31 235
Notice that October data begins at 10 October, whereas subsequent months have complete data.
I need to get the average monthly sales over all complete months, which in this case would be November and December 2011.
How would I do this?