One database field needs to be restricted to only those values that are single alphanumeric symbols.

Integer fields are designed to store whole numbers without decimal points. They cannot accommodate alphanumeric symbols, as integers are strictly numerical and do not support any alphabetic characters. Therefore, this choice fails to meet the requirement of allowing single alphanumeric symbols.

Floating point fields are used to store numbers that require decimal representation. Similar to integers, they are exclusively numerical and do not allow for the inclusion of alphabetic characters. This limitation makes floating point fields unsuitable for the task of restricting values to single alphanumeric symbols.

Character string fields can hold multiple characters, allowing for combinations of letters and numbers. However, since the requirement is to restrict input to single symbols, character strings do not fit the criteria. They permit more than one character, thus failing to enforce the restriction to single alphanumeric symbols.