有时候在计算的时候才发现数据类型错了，算不出来，下面是几点注意：
If you use "Modify Table" to change a field type from real
to integer, you are re-writing the table -- the new table
has now an integer column in place of the real column. Values
will be rounded to the nearest integer. Any decimal precision
will be lost. If you merely want to "display" your values
as integers you can select the number of decimals to display
in the "Display" section of the "Modify Table" dialog box.
You can also use the "Column Settings" command under the
"Dataview" menu to set a desired "format" for numbers, including
setting the number of decimals.
Additionally, if you want to use a "Formula Field" there is
the "RealToInt()" (shorthand: "R2I()") function.
