Slideshow:
Laws involving the grouping
(γ) operator
- interaction with duplicate elminiation
(δ)
Laws involving the grouping
(γ) operator
- interaction with duplicate elminiation
(δ)
Laws involving the grouping
(γ) operator
- interaction with projection
(π)
- The grouping operator
interact with very few
relation algebra operations:
- γL produces
a set,
therefore the
δ operation is
unnecessary:
Example:
- You can project out
some attributes as long as
you keep the
grouping attributes:
- If aggregate function
L = max
or
L = min,
then we can
remove
duplicate values:
- γL produces
a set,
therefore the
δ operation is
unnecessary: