Sure! Let's analyze the concept of tuples and how they handle missing values in databases.
In databases, tuples represent records, and each attribute of the record corresponds to a field. Sometimes, a record might not have a value for a specific attribute. In this context, here's a breakdown of the possible values:
a. Unknown: This implies that the value for the attribute is not known at the moment. However, it does not imply absence of value, but rather a lack of information.
b. Not Applicable: This means that the attribute does not apply to this particular record. For example, a field for "Spouse's Name" might be "Not Applicable" for an unmarried person.
c. Null: This is a special marker used in databases to indicate that a value does not exist for the attribute in that record. It is different from zeros, empty strings, and any other value; it's a distinct value that signals the absence of data.
d. Zero: This is a numeric value indicating nothing or the absence of something, but it is different from null as zero is a definite value.
Given these definitions, the correct value that a tuple takes when a record does not have a value for an attribute is:
c. Null.
