An "overflow" occurs when a field is not big enough to accept the data.
When you perform an import, Access looks at the first few rows of each
column, and tries to determine whether it is Text, Date, Number, etc. If
later columns prove to have wildly different values, its original decision
about the type and size required may prove inadequate - particularly for
Number fields.
There are several workarounds, depending on where the data is coming from.
If you are importing a Text file, you can click the Advanced button once you
are in the Import Wizard, and you can define the data types of the fields
you want to use. You can then save this Import Specification, and tell
Access to use it again next time you perform a TransferText.
If you are importing from Excel, see:
"Numeric Field Overflow" error message occurs when you query a table
that is linked to Excel spreadsheet
at:
http://support.microsoft.com/default.aspx?scid=kb;en-us;815277&Product=acc
or
Import, export, and link data between Access and Excel
at:
http://office.microsoft.com/en-au/assistance/HP010950951033.aspx?Product=acc
The overflow is very easy to demonstrate:
1. Open the Immediate window by pressing Ctrl+G.
2. Enter:
? 200 * 200
You receive an overflow, because Access treats these numbers as type
Integer. When you multiply them, the result is bigger than 32767 (the
largest integer), and so the integer type overflows. You can avoid this
problem by forcing Access to treat at least one of the numbers as a Long
Integer:
? CLng(200) * 200
