Question at position 36 A referential integrity constraint specifies that the existence of an attribute in one table depends upon the existence of a foreign key in the same or another table.TrueFalse

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BlackTom AI · Accepted Answer

The question asks about a referential integrity constraint and presents the statement: 'The existence of an attribute in one table depends upon the existence of a foreign key in the same or another table.'
Option 1: True. Interpreting this, one might think that the presence of a value in a child table (the foreign key attribute) depends on there being a corresponding value (a primary key) in the parent table. In practice, referential integrity requires that a foreign key value either matches an existing primary key in the referenced table or is null (if nulls are allowed). This means the validity of the foreign key value is contingent on the existence of a matching key in the parent table, which can be read as the child attribute depending on another table's data. However, the phrasing mentions the 'existence of a foreign key' rather than the 'existence of a matching primary key value' and may be interpreted as conflating the foreign key attribute with the constraint itself rather than the referential linkage. This makes the statement somewhat awkward and potentially misleading if taken literally.
Option 2: False. A clearer way to express referential integrity is that a foreign key value in a child table must either be null (if allowed) or reference an existing primary key value in the parent table. The constraint governs the relationship between tables, not the mere existence of a foreign key independent of its referenced key. The dependence is on the referenced key's existence (in the parent table) rather than on the mere presence of a foreign key attribute. Moreover, referential integrity does not demand the existence of a separate 'foreign key' in the same table; the foreign key is the attribute in the child table that participates in the constraint, and its validity hinges on the parent key.
In summary, while there is a dependency introduced by the constraint between rows in the child and parent tables, the way the statement is worded can be misleading. The precise mechanism is that a foreign key value must reference an existing primary key in the related table (or be null, if allowed), rather than asserting that the mere existence of a foreign key is the constraint itself. This makes the statement, taken literally as written, problematic and generally considered not a correct characterization of referential integrity.

Question at position 36 A referential integrity constraint specifies that the existence of an attribute in one table depends upon the existence of a foreign key in the same or another table.TrueFalse

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