RENAME (Relational Algebra)

The RENAME operation, $\rho$, is used to rename attributes of a relation or the relation name or both. It is useful when a query requires multiple operations and is necessary in some cases. There are three possible cases:

• Change relation name to $S$: ${\rho }_S(R)$
• Change column (attribute) names to $B_1,B_2,\dots ,B_n$: ${\rho }_{(B_1,B_2,\dots ,B_n)}(R)$
• Change combined attribute and relation names: ${\rho }_{S(B_1,B_2,\dots ,B_n)}(R)$

Example:

• Apply multiple operations and rename (using $S\leftarrow R$): $TEMP\leftarrow {\sigma }_{DNO=5}(EMPLOYEE)$ $R(\text{First\_name, Last\_name, Salary})\leftarrow {\pi }_{\text{FNAME, LNAME, SALARY}}(TEMP)$