In relational algebra, a rename is a unary operation written as where:
The result is identical to R except that the b attribute in all tuples is renamed to a.[1] For an example, consider the following invocation of ρ on an Employee relation and the result of that invocation:
|
|
Name
|
EmployeeId
|
Harry
|
3415
|
Sally
|
2241
|
|
EmployeeName
|
EmployeeId
|
Harry
|
3415
|
Sally
|
2241
|
|
Formally, the semantics of the rename operator is defined as follows:
where is defined as the tuple t, with the b attribute renamed to a, so that: