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. 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: