The query cache stores the text of a SELECT query together with the corresponding result that was sent to the client. If an identical query is received later, the server retrieves the results from the query cache rather than parsing and executing the query again.
The query cache is extremely useful in an environment where you have tables that don’t change very often and for which the server receives a lot of identical queries. This is a typical situation for many Web servers that generate a lot of dynamic pages based on database content.
