問題文
A formula must return the word Missing when a text field on the record has never been filled in, and must treat a field containing only an empty string the same way. Which function is the appropriate choice, and why?
選択肢
- BLANKVALUE, because it returns a substitute value and therefore also reports whether the field was empty when the record was read.
- ISBLANK, because it returns true both for fields that contain no value and for text fields that contain an empty string.
- LEN, where a length of zero always means the field was never filled in.
- ISNULL, the general-purpose emptiness test for every field type, while ISBLANK works only on number, currency, and percent fields, which is why ISNULL is recommended for text comparisons.