这是mysql 的select 执行过程more
->starting
->Waiting for query cache lock
->checking query cache for query
->checking permissions
->opening tables
->system lock
->init
->optimizing
->statistics
->preparing
->creating tmp table
->executing
->copying to tmp table
->sorting result
->sending data
->end
->removing tmp table
->query end
->closing tables
->freeing items
->storing result in query cache
->logging slow query
->cleaning up
这是个多表查询的一个语句的完整执行过程