Rename (relational algebra) - Alchetron, the free social encyclopedia

In relational algebra, a rename is a unary operation written as ρ a / b ( R ) where:

R is a relation

a and b are attribute names

b is an attribute of R

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 E m p l o y e e relation and the result of that invocation:

Formally the semantics of the rename operator is defined as follows:

ρ a / b ( R ) = { t [ a / b ] : t ∈ R }

where t [ a / b ] is defined as the tuple t with the b attribute renamed to a so that:

t [ a / b ] = { ( c , v ) | ( c , v ) ∈ t , c ≠ b } ∪ { ( a , t ( b ) ) }

References

Rename (relational algebra) Wikipedia

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