Oracle SQL Quiz
The following questions are purely for you to
measure your level of understanding. After
reading each of the following questions, answer
the question in your own words. Post your
answers on the discussion forum, and read other
navigational data language requires
knowledge of the internal tables and index
structures. SQL is a better database access
language because the SQL optimizer takes
care of the internal navigation.
the difference between a declarative
data access language and a navigational
data access language?
The order that the tables will be
The choice of indexes
The internal joins methods (sort
merge, hash, nested loops).
The method to sort the result set
(use an index or invoke a sort)
decisions does the SQL optimizer need to
make when deciding upon the optimal
independence means that related tables can
be joined at any time without having to
pre-establish the relationship. Hence, any
two tables will a common column can be
joined together at runtime.
data independence an important feature
of relational databases and SQL?
optimizer modes have different goals and
different internal weights. The all_rows
goal favors full-table scans and
minimization of machine resources while the
first_rows optimizer goal favors index-scans
and return data back to the requestor as
soon as possible.
the choice of the SQL optimizer goal an
important consideration when tuning an
introducing redundancy into the data model
(denormalization) expensive table joins can
database design important to SQL
performance? How can databases be
designed to make SQL statements run
optimizer gets confused or cannot find an
appropriate index that matches the WHERE
clause, the optimizer will read every row in
the table. Hence large-table full-table
scans often indicate a missing index or a
sub-optimal choice of optimizer goal.
searching for large-table full-table
scans critical to SQL tuning?
purpose of indexes is to make SQL queries
run faster. If the optimizer detects an
indexes that matches part of the WHERE
clause of the query, then the optimizer will
use the index to avoid having to read every
row in the table.
the relationship between indexes and SQL