MySQL Example Scripts for “Partial Results”

This section contains the create and insert statements to run the examples from Chapter 7, “Partial Results” in a MySQL database.

Querying Top-N Rows

An indexed Top-N query doesn’t show a “filesort” operation in the Extras column:

SELECT *
  FROM sales
 ORDER BY sale_date DESC
 LIMIT 10

+----+-------+-------+-------------+--------+-------+
| id | table | type  | key         | rows   | Extra |
+----+-------+-------+-------------+--------+-------+
|  1 | sales | index | sales_dt_pr | 836092 |       | 
+----+-------+-------+-------------+--------+-------+