Editing Relational algebra (section)

== Rename ==
{{Main|Rename (relational algebra)}}
A '''rename''' (''ρ'') is a [[unary operation]] written as <math>\rho_{a / b}(R)</math> where the result is identical to ''R'' except that the ''b'' attribute in all tuples is renamed to an ''a'' attribute.  This is commonly used to rename the attribute of a [[relation (database)|relation]] for the purpose of a join.

To rename the "isFriend" attribute to "isBusinessContact" in a relation, <math>\rho_{\text{isBusinessContact / isFriend} } ( \text{addressBook} )</math> might be used.

There is also the <math>\rho_{x(A_1, \ldots,A_n)}(R)</math> notation, where ''R'' is renamed to ''x'' and the attributes <math>\{a_1,\ldots,a_n\}</math> are renamed to <math>\{A_1,\ldots,A_n\}</math>.<ref>{{Cite book|last=Silberschatz|first=Abraham |title=Database system concepts|date=2020 |author2=Henry F. Korth |author3=S. Sudarshan|isbn=978-0-07-802215-9|edition=Seventh |location=New York |oclc=1080554130|page=56}}</ref>