Consider the following relational database schema:
- EMP (eno name, age)
- PROJ (pno name)
- INVOLVED (eno, pno)
EMP contains information about employees. PROJ about projects and involved about which employees involved in which projects. The underlined attributes are the primary keys for the respective relations.
What is the relational algebra expression containing one or more of $\{ \sigma, \pi, \times, \rho, -\}$ which is equivalent to SQL query.
select eno from EMP|INVOLVED where EMP.eno=INVOLVED.eno and INVOLVED.pno=3