Question

What datatype can't be used in a primary key, DISTINCT, GROUP BY, ORDER BY, or in joins?

a) INTEGER
b) VARCHAR
c) INTERVAL DAY(n1) TO SECONDS(n2)
d) DECIMAL

Answer 1

The datatype that cannot be used in operations requiring a stable sorting or unique identification, such as primary keys and set operations, is c) INTERVAL DAY(n1) TO SECONDS(n2) due to its variable representation of time spans.

Step-by-step explanation:

The datatype that can't be used in a primary key, DISTINCT, GROUP BY, ORDER BY, or in joins is c) INTERVAL DAY(n1) TO SECONDS(n2). This is because the INTERVAL type represents a span of time and doesn't have a consistent, precise sorting order as an INTEGER, VARCHAR, or DECIMAL does. These other types can represent discrete values that can be easily compared and sorted. An INTERVAL can vary widely in its representation and thus is not suitable for operations that require a stable, definitive sorting or unique identification like those needed for a primary key or in set operations.

The datatype that cannot be used in a primary key, DISTINCT, GROUP BY, ORDER BY, or in joins is INTERVAL DAY(n1) TO SECONDS(n2).