Defining the Null Value for an Import Operation
The default value for this option is ?. This means a question mark character is used to represent a null value resulting
SELECT statement. This string is also used in an import file to indicate that the corresponding
column should be assigned a null value.
Many spreadsheet and database applications can save data in tab delimited format. In most cases, they do not allow you to specify a null character, but simply write nothing to the file. If you want to import data from a file like this, set this field to a zero length string by deleting the contents of the field.
1 Select Tools > Options.
2 Select the Data Format tab.
3 In the field Display this string for Null data fields, fill in the string desired.
Use the string you have defined for the display of NULL values. The default is a question mark (?). This string, possibly quoted, should be the only thing between the surrounding delimiter characters.