Database Systems

Express RS ((Left outer join) using a subset of the following relational algebra operations (Project, Select, Rename, Union, Intersection, Set Difference, Cartesian product, Join (conditional or natural)). Explain your assumptions, if any. We assume that attributes of S is denoted as ATTR(S), attributes of R is denoted as ATTR(R) and (ATTR(R)-ATTR(S) denotes a set of attributes in R that does not belong to S. We also use the notation Mal,a2,a3,,an(NULL) to denote a relation M with attributes ( a1,a2, a3, ..an) with one tuple whose values are null for all attributes. For example Mid,name (NULL) will be