Question

what is significance of using allow zero length property

Answer 1

Hello

Here is the answer

Nulls and Zero-Length Strings

Relational databases support a special value in fields, called a Null, that indicates an unknown value. In contrast, you can set Text and Memo fields to a zero-length string to indicate that the value of a field is known but the field is empty.

Explanation:

Why is it important to differentiate Nulls (unknown values) from zero-length strings? Here's an example: Suppose you have a database that stores the results of a survey about automobile preferences. For questionnaires on which there is no response to a color-preference question, it is appropriate to store a Null. You don't want to match responses based on an unknown response, and you don't want to include the row in calculating totals or averages. On the other hand, some people might have responded "I don't care" for a color preference. In this case, you have a known "no preference" answer, and a zero-length string is appropriate. You can match all "I don't care" responses and include the responses in totals and averages.