Consider the relational schema given below, where eId of the relation dependent is a foreign key referring to empId of the relation employee. Assume that every employee has at least one associated dependent in the dependent relation.
- employee (empId, empName, empAge)
- dependent (depId, eId, depName, depAge)
Consider the following relational algebra query:
$\Pi_{empId}\:(employee) - \Pi_{empId}\:(employee \bowtie_{(empId=eID) \wedge (empAge \leq depAge)} dependent)$
The above query evaluates to the set of empIds of employees whose age is greater than that of
- some dependent.
- all dependents.
- some of his/her dependents.
- all of his/her dependents.