finding the minimum and maximum in tuples (database) -


consider relation r number of tuples of r n. how can find minimum , maximum possible sizes (in tuples) result relation produced following relational algebra expressions? please help..

(1) σa=5 , b=5(r)      (2) Πa,b(r)

(a,b random names of attribute)

σ means select , Π project...

"how can find ..."

restrict filters out tuples input. can filter out 0 tuples in total ? less 0 tuples ? can filter out n tuples in total ? more n ?

similar reasoning projection.


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