Consider the following relational schema:
emp(eid, ename, deptid)
dept(deptid, dname, lid)
loc(lid, city)
Consider the following relational algebra query:
\(\Pi _{ename}(\sigma _{city\text{ = 'Mumbai'}\bigvee \text{'Delhi'}} ((emp ⋈ dept) ⋈ loc))\)
The above query evaluates:
1
All employee names who lives in Mumbai and Delhi.
2
All employee names whose department is in Mumbai or Delhi.
3
All employee names and id who lives in Mumbai or Delhi.
4
All employee names,employee id and department id who lives in Mumbai and Delhi.