Is your NAV on C/SIDE (native) or SQL Server? Well, anyway, yes in NAV exists a “virtual table” named “Field” (2000000041) which contains al the master-defintions of all fields. As this is an internal/virtual system table, this does not realy exist as table on SQL Server site; you only can access it from NAV.
With SQL there is indeed a character conversion, e.g. a “.” (dot) will be converted to “_” (underline).
But: the field 64 “Inv. Discounts (LCY)” in table 18 “Customer” is a FlowField. This means it is used to display data taken from other sub-sequent tables; in this case it is summing up the field ".“Inv. Discount (LCY)” from table 21 “Cust. Ledger Entry”.
Hence, FlowFields actually do not contain any data! On the SQL site table definition it doesn’t even exist! Thus, FlowFields cannot be accessed via ODBC; you have to fetch the required data from the subsequent table (e.g. “Cust. Ledger Entry”).
And of course you cannot write data into FlowFields …
This is one reason why i allways name fields without spaces and special characters - only English letters are used. E.g. “Inv. Discounts (LCY)” will be InvDiscLcy; but caption will be “Inv. Discounts (LCY)”.