Pushing selects, which moves the relational selection earlier, is a choice that

Question

Pushing selects, which moves the relational selection earlier, is a choice that is made during a) Query parsing time b) Query planning time c) Query plan optimization time d) Query plan execution time e) None of these What database feature improves performance the most? a) Joins b) Transactions c) Write-ahead logging d) Indexes e) Views If you have a B+ tree with an order of 80, how many keys will each interior (non-leaf) node have? With a B+ tree of order 15, how many keys will each root node contain? In a B+ tree node that has 4 keys, how many ranges are defined? There is no difference between clustered and unclustered indexes when it comes to: a) Joins involving a foreign key b) Range search c) Grouping of results d) Exact search e) Sorting of results The PRIMARY KEY constraint is a combination of what two other constraints? ___ and___ The relational algebra operator is associated to which part of an SQL query: a) The WHERE clause b) The join c) The aggregation functions d) The GROUP BY /HAVING clause e) None of these

Explanation / Answer

Let's go with the easiest one first.

27. The PRIMARY KEY constraint is a combination of UNIQUE and NOT NULL constraints. Since we use primary key to identify a row in db it has to unique and it should not be a null value else the primary purpose of it is defeated.

22. Indexes

21. Query plan optimisation time

28. Natural join operator is related to 'the join' from options.

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