Consider the following relational database.
employee (person name, street, city )
works (person name, company name, salary)
company (company name, city)
manages (person name, manager name)
The tuple calculus expression equivalent to the following relational algebra expression:
\({{\rm{\Pi }}_{person\;name,\;city}}\left( {employee⋈\left( {{\sigma _{company\;name = 'ABC'}}\left( {works} \right)} \right)} \right)\)
1
{t | ∃ r ∈ employee ∃ s ∈ works ( t[person-name] = r[person-name] ∧ t[city] = r[city] ∧ s[company-name] = “ABC”)}
2
{t | ∃ r ∈ employee ∃ s ∈ works ( t[person-name] = r[person-name] ∧ t[city] = r[city] ∧ r[person-name] = s[person-name] ∧ s[company-name] = ‘ABC’)}
3
{t | ∃ r ∈ employee ∃ s ∈ works (r[person-name] = s[person-name] ∧ s[company-name] = ‘ABC’)}
4
None of the above