Projection (relational algebra)

In relational algebra, a projection is a unary operation written as Π a 1 , . . . , a n ( R ) {displaystyle Pi _{a_{1},...,a_{n}}(R)} where a 1 , . . . , a n {displaystyle a_{1},...,a_{n}} is a set of attribute names. The result of such projection is defined as the set obtained when the components of the tuple R {displaystyle R} are restricted to the set { a 1 , . . . , a n } {displaystyle {a_{1},...,a_{n}}} – it discards (or excludes) the other attributes. In relational algebra, a projection is a unary operation written as Π a 1 , . . . , a n ( R ) {displaystyle Pi _{a_{1},...,a_{n}}(R)} where a 1 , . . . , a n {displaystyle a_{1},...,a_{n}} is a set of attribute names. The result of such projection is defined as the set obtained when the components of the tuple R {displaystyle R} are restricted to the set { a 1 , . . . , a n } {displaystyle {a_{1},...,a_{n}}} – it discards (or excludes) the other attributes.