The LIMIT ROWS EXAMINED
clause is a good way to minimize the overhead of a very large or otherwise expensive query if we don't necessarily want or need to search every row in a large table or set of tables.
Import the ISFDB
database as described in the Importing the data exported by mysqldump recipe, earlier in this chapter.
Open a terminal window and launch the
mysql
command-line client and connect to theisfdb
database.Run the following query from the Using SHOW EXPLAIN with running queries recipe, with one small addition at the end:
SELECT titles.title_id AS ID, titles.title_title AS Title, authors.author_legalname AS Name, (SELECT COUNT(DISTINCT title_relationships.review_id) FROM title_relationships WHERE title_relationships.title_id = titles.title_id) AS reviews FROM titles,authors,canonical_author WHERE (SELECT COUNT(DISTINCT title_relationships.review_id) FROM title_relationships...