An orchestra database consists of the following relations:
CONDUCTS (conductor, composition)
REQUIRES (composition, Instrument)
PLAYS (Player, Instrument)
Give the relational calculus queries for the following:
(i) List the compositions and the players.
(ii) List the compositions which require the ‘violin' and the ‘congo'

Ans: (i) Tuple Calculus:
{r[Composition] || p[Player] | r ∈ REQUIRES ∧ p ∈ PLAYS
∧ r[Instrument] = p[Instrument]}
Domain Calculus:
{c || p | ∃i1, i2 ( ∈ REQUIRES ∧ ∈ PLAYS ∧ i1 = i2)}
(ii) Tuple Calculus:
{r[Composition] | r ∈ REQUIRES ∧ ∃u (u ∈ REQUIRES
∧ r[Composition] = u[Composition] ∧ r[Instrument] = ‘violin'
∧ u[Instrument] = ‘congo')}
Domain Calculus:
{c | ∃i1, c2, i2 ( ∈ REQUIRES ∧ ∈ REQUIRES
∧ c1 = c ∧ i1 = ‘violin' ∧ i2 = ‘congo')}