What are the main rules of query optimization? I. Execute selections and projections as soon as possible. II. Execute operations whose selectivity...
What are the main rules of query optimization?
I. Execute selections and projections as soon as possible.
II. Execute operations whose selectivity results in the smallest number of blocks to be read from disk first.
III. Combine selection with Cartesian product forming a join, when possible.
IV. Evaluate common sub-expressions and store their results if it is more efficient to read them than to reprocess them.
a) I and II are correct.
b) I, II, and III are correct.
c) I, III, and IV are correct.
d) II, III, and IV are correct.
I. Execute selections and projections as soon as possible.
II. Execute operations whose selectivity results in the smallest number of blocks to be read from disk first.
III. Combine selection with Cartesian product forming a join, when possible.
IV. Evaluate common sub-expressions and store their results if it is more efficient to read them than to reprocess them.
a) I and II are correct.
b) I, II, and III are correct.
c) I, III, and IV are correct.
d) II, III, and IV are correct.
💡 1 Resposta
Ed 
As principais regras de otimização de consulta são: I. Execute seleções e projeções o mais cedo possível. II. Execute operações cuja seletividade resulte no menor número de blocos a serem lidos do disco primeiro. III. Combine seleção com produto cartesiano formando um join, quando possível. IV. Avalie sub-expressões comuns e armazene seus resultados se for mais eficiente lê-los do que processá-los novamente. A alternativa correta é a letra c) I, III e IV estão corretas.
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