Suppose we have 2 relation schemas. Enrolled (Sid, Gid) and course (Gid). Then which of the relation algebra query gives us “Sids of students enrolled for every course”.
1
\({\pi _{sid}}\left( {{\pi _{sid}}\left( E \right) \times C} \right)\)
2
\({\pi _{sid}}\left( {{\pi _{sid}}\left( E \right) \times C - E} \right)\)
3
\({\pi _{sid}}\left( E \right) - {\pi _{sid}}\left( {{\pi _{sid}}\left( E \right) \times C - E} \right)\)
4
None of these