Sams Teach Yourself SQL in 24 Hours, Second Edition

Hour 17, "Improving Database Performance"

Quiz Answers

1:	Would the use of a unique index on a small table be of any benefit?
A1:	The index may not be of any use for performance issues; but, the unique index would keep referential integrity intact. Referential integrity is discussed in Hour 3, "Managing Database Objects."
2:	What happens when the optimizer chooses not to use an index on a table when a query has been executed?
A2:	A full table scan occurs.
3:	Should the most restrictive clause(s) be placed before the join condition(s) or after the join conditions in the WHERE clause?
A3:	The most restrictive clause(s) should be evaluated before the join condition(s) because join conditions normally return a large number of rows.

Exercise Answers ...