when since database joins expensive?


i'm doing investigate databases i'm looking during prerequisites relational dbs.



i'm removing joins infinite tables unequivocally expensive, nonetheless i'm totally certain why. does dbms need govern join operation, where bottleneck?

how denormalization assistance overcome expense? optimization techniques (indexing, example) help?



personal practice welcome! you're going post links resources, greatfully prevaricate wikipedia. i know where already.



in union this, i'm wondering denormalized approaches used cloud use databases bigtable simpledb. .



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