Rechercher dans le manuel MySQL
8.8 Understanding the Query Execution Plan
Depending on the details of your tables, columns, indexes, and the
conditions in your WHERE clause, the MySQL
optimizer considers many techniques to efficiently perform the
lookups involved in an SQL query. A query on a huge table can be
performed without reading all the rows; a join involving several
tables can be performed without comparing every combination of
rows. The set of operations that the optimizer chooses to perform
the most efficient query is called the “query execution
plan”, also known as the
EXPLAIN plan. Your goals are to
recognize the aspects of the
EXPLAIN plan that indicate a query
is optimized well, and to learn the SQL syntax and indexing
techniques to improve the plan if you see some inefficient
operations.
Document created the 26/06/2006, last modified the 26/10/2018
Source of the printed document:https://www.gaudry.be/en/mysql-rf-execution-plan-information.html
The infobrol is a personal site whose content is my sole responsibility. The text is available under CreativeCommons license (BY-NC-SA). More info on the terms of use and the author.
References
These references and links indicate documents consulted during the writing of this page, or which may provide additional information, but the authors of these sources can not be held responsible for the content of this page.
The author This site is solely responsible for the way in which the various concepts, and the freedoms that are taken with the reference works, are presented here. Remember that you must cross multiple source information to reduce the risk of errors.
