Execution time in mysql changes

[cmps]

Hey all,
I would like to know why when having big data in mysql table, executing a query for the first time takes 0.1.. sec, but if executing again the same query later, it will take only 0.0006 sec ?
Exemple:
SELECT name FROM users where id > 310000 limit 20
takes: 0.1844 sec the first time executed
and it takes: 0.0006 sec when excecuted again

Is there caching or data management ?
The speed will stay permanently ~0.0006 after executing it for the first time ?

Thank you :)

[cereal]

Yes, there are different caches, check the documentation for more information:

• http://dev.mysql.com/doc/refman/5.5/en/query-cache.html
• http://dev.mysql.com/doc/refman/5.5/en/query-cache-status-and-maintenance.html
• http://dev.mysql.com/doc/refman/5.5/en/buffering-caching.html

And there are some limitations, as the subqueries cannot be cached:

• http://dev.mysql.com/doc/refman/5.5/en/query-cache-operation.html

But if you use MariaDB, which is a fork of MySQL, you can cache even those queries:

• https://mariadb.com/kb/en/subquery-cache/