Which of the following statements about indexes is true?
Indexes take up too much space on disk and should not be used.
Not having any indexes can make your queries run slowly.
You should index as many columns as possible.
None of the above.
When choosing data types for columns
use the same ones throughout a database because this will make the database more efficient
use variable- sized ones wherever possible to optimize disk usage
use fixed-sized ones wherever possible to speed up access to data
none of the above
When choosing storage engine types for tables
always use InnoDB or BDB because they are transaction safe
always use MyISAM because it is the fastest
use a mix of types depending on what you need in a table
An index will not be used if a query
uses a leftmost prefix of the index columns
uses all the index columns in a different order than in the index
uses all the index columns in the same order as in the index
uses a rightmost prefix of the index columns
Use OPTIMIZE TABLE
when you have just created a table, to improve its structure
when using InnoDB tables, to reduce overhead
after a lot of SELECT statements have been run on a table
after a lot of DELETE statements have been run on a table
