The following relation records the age of 500 employees of a company, where $empNo$ (indicating the employee number) is the key: $$empAge(\underline{empNo}, age)$$ Consider the following relational algebra expression: $$\Pi_{empNo}(empAge \bowtie_{(age > age1)} ho_{empNo1, age1}(empAge))$$ What does the above expression generate?

Let us analyze the given relational algebra expression step by step:

1. Renaming: $ho_{empNo1, age1}(empAge)$ creates a copy of the relation $empAge$ with attributes renamed to $(empNo1, age1)$.

2. Theta Join: The join condition is $age > age1$:

   $$empAge \bowtie_{(age > age1)} ho_{empNo1, age1}(empAge)$$

   This condition pairs an employee from the first relation with any employee in the second relation who has a strictly smaller age.

3. Condition for inclusion: A tuple from $empAge$ appears in this join result if and only if there exists at least one tuple in the relation whose age is strictly less than this employee's age ($age > age1$).

   • For an employee with the minimum age, there is no employee in the table with an age strictly less than theirs. Thus, their tuple fails the join condition and does not appear in the result.

   • For every other employee (whose age is strictly greater than at least one other employee), their tuple satisfies the condition and is included.

4. Projection: $\Pi_{empNo}(\dots)$ selects the employee numbers ($empNo$) of all tuples surviving the join.

Therefore, the expression returns the employee numbers of all employees whose age is not the minimum, which corresponds to option (C).